The phrase parlour socialist (American English parlor socialist) designates a middle- or upper-class person claiming to be committed to the cause of socialism but not actually involved in the achievement of that cause.

The phrase parlour socialism (American English parlor socialism) designates the claimed commitment of a middle- or upper-class person to the cause of socialism without actual involvement in the achievement of that cause.

—Cf. also:
– ‘parlour’ (attributive modifier): ‘parlour patriot’
– ‘armchair’ (attributive modifier)
– ‘limousine liberal’: meaning and early occurrences
– ‘champagne socialist’: meanings and early occurrences

The texts containing the earliest occurrences of parlour socialist and parlor socialist that I have found indicate that, in early use:
– In British English, parlour socialist was quasi-synonymous with club socialist;
– In American English, parlor socialist and parlor revolutionist were contrasted with beer-room socialist, beer-hall socialist, beer-house socialist and beer-house revolutionist, which probably designated a lower-class person claiming to be committed to the cause of socialism. All those phrases were reportedly used in particular by the U.S. Republican statesman Theodore Roosevelt (1858-1919), 26^th President of the USA from 1901 to 1909, who at that time was the president of the New York City Board of Police Commissioners.

These are the earliest occurrences of parlour socialist, parlor socialist and parlour socialism that I have found, in chronological order:

1-: parlour socialism—from The Morning Post (London, England) of Wednesday 19^th July 1893—here, parlour socialism may have no negative connotation:

M. ZOLA’S LAST NOVEL.
FROM OUR CORRESPONDENT.

Paris, July 15.
“Le Docteur Pascal,” M. Zola’s ¹ latest novel, is the concluding volume of the Rougon Macquart Series—“the social and political history of a family under the Second Empire”— and brings to an end the indefatigable and systematic labour of over twenty years. Its publication has been one of the chief literary events of the season, and was duly and very gracefully honoured by M. Charpentier, the publisher of M. Zola’s works, by an open-air entertainment given to about two hundred guests in the Bois de Boulogne. […] There were Catulle Mendes ², with long, flowing, grizzly locks, broad Parnassian forehead, and delicately-curved nose, who read some eulogistic lines; Séverine ³, with henna-tinted hair, tied in a queue, and a Parisian elegance of costume, which hardly indicated the prophetess of parlour Socialism; Octave Mirbeau ⁴, red-faced, red-haired, straw-hatted, more like a bookmaker than a literary astronomer and discoverer of new Shakespeares; [&c.].

¹ Émile Zola (1840-1902) was a French novelist and critic. His series of twenty novels collectively entitled Les Rougon-Macquart (1871-93) attempts to show how human behaviour is determined by environment and heredity.
² Catulle Mendès (1841-1909) was a French poet, playwright and novelist, most noted for his association with the Parnassians, a group of French poets who advocated the idea of art for art’s sake in reaction to the formlessness of Romanticism.
³ Séverine was the pen name of the French socialist journalist Caroline Rémy (1855-1929).
⁴ Octave Mirbeau (1850-1917) was a French journalist, playwright and novelist.

2-: parlour socialist and club socialist [cf. also 8 below]—from an appeal published in Justice: The Organ of the Social Democracy (London, England) of Saturday 28^th September 1895—here, parlour socialist and club socialist do not seem to be used derogatorily:

TO OUR SYMPATHISERS.

It is often said that outside the ranks of the S.D.F. ⁵ there are a large number of men and women, who sympathise with our aims and objects, who for various reasons do not see their way to join the body, but who are nevertheless ready to assist the movement financially. […] The present is a most opportune time for such persons to come forward and materially assist the Federation in adopting and carrying through a go-ahead policy.
[…]
[…] Our very growth makes our responsibility greater, and means more and more work and consequently a greater need for money. In this latter respect our outside friends should be able to help, and help very materially. It is comparatively easy to be a club or parlour Socialist, but to be a working member of the S.D.F. is no light matter. Many men and women are paying weekly what to them are large subscriptions, and at the same time giving their leisure to the work. These are unable to pay more than they do now, and therefore the money for the new work to be undertaken must come from a new source.

⁵ S.D.F. is the abbreviation of Social-Democratic Federation.

3-: In the accounts of a public meeting of the Members and Friends of the City Vigilance League of New York, published on Tuesday 10^th November 1896:

3.1-: parlor socialist and beer-room socialist—from The Brooklyn Citizen (Brooklyn, New York) and in The Sun (New York City, New York)—here, parlor socialist and beer-room socialist are used derogatorily:

[Dr. Parkhurst ⁶] introduced Mr. Roosevelt, who early in his speech spoke of “parlor Socialists,” meaning the reformers who stay at home and criticise persons and measures. He said they were only a shade less objectionable and quite as much of a nuisance as the beerroom Socialists.

⁶ Charles Henry Parkhurst (1842-1933) was a U.S. clergyman and social reformer who exposed the corruption in both the government and the police department of New York City.

3.2-: parlor socialist—from The New York Times (New York City, New York)—here, parlor socialist seems to simply connote idealism:

Dr. Parkhurst next introduced President Roosevelt of the Police Board. He eulogized his colleague, Commissioner Andrews, and Charles G. Wilson, President of the Health Board, and spoke of the practical results of their work.
“If men who are parlor socialists,” he said, “and spend their time talking visionary schemes would investigate the practical methods in use in some of the city departments it would be a good thing.”

4-: parlor socialist, beer-house socialist, parlor revolutionist and beer-house revolutionist—from The Sun (New York City, New York) of Friday 20^th November 1896—here, those four phrases are used derogatorily:

Theodore Roosevelt talked entertainingly for nearly an hour yesterday afternoon in Hope Chapel, 339 East Fourth street, at a meeting of the Federation of East Side Workers. His subject was “Philanthropy and Municipal Life.” […] The Rev. John B. Devins, President of the federation, asked Mr. Roosevelt to speak to them.
[…]
“I especially believe in intelligent philanthropy; for its field of operation is being constantly and indefinitely enlarged by unintelligent philanthropy. I have the greatest respect for those who strive intelligently, but there is nothing more noxious than the parlor Socialist or revolutionist. He is as bad as the ordinary beer-house Socialist or revolutionist, with his preaching of vague discontent, without taking the trouble of finding out how justifiable it is and how it can be remedied.”

5-: parlor socialist and beer-hall socialist—from The Knoxville Journal (Knoxville, Tennessee) of Tuesday 24^th November 1896—here, parlor socialist and beer-hall socialist are used derogatorily:

AIR “POWERS.”

Confidence in “horse sense,” the fine contempt for the air fighter and the picnic if not the parlor socialist, have swerved the two great states of Kansas and Nebraska as completely out of the track of national progress as if they had seceded—as one of them proposes to do in its financial system—to the republic of Mexico. We laughed at the notion of “Sockless” Simpsons and Mrs. Leases and Whiskered Peffers and Boy Orators running off with two of the most “intelligent” of American commonweaths [sic]. Perhaps the national sense of humor is less acute than it was. At any rate, the laughter was inefficacious.
Education will meet the evil. But more than education is needed. Plainly our society has reached that age when, as in the elder world, it must hold every man strictly responsible for his words. If the “parlor socialist” talks like the “beer-hall socialist” he should be shunned as the beer-hall socialist is shunned. It is class privilege of the worst sort that John Brisben Walker should have a hearing that is denied to Johann Most. And the same is true of the agitator in print as of the agitator in talk. There is scarcely a review in the country which will not make of its pages a platform from which any demagogue may “fight the air”—so be it there is a profitable popular interest in his gyrations. As for newspapers, there is not a great city in the Union which has not at least one which cannot discuss the price of coal or clothing, the closing hours of saloons or the functions of a bank without a ranting appeal to mass prejudice. It seems to catch a good many greasy pennies, or else it would not be kept up. One would suppose that it would grow as nauseating as the liquor which is put in a dipsomaniac’s food.
All these men, even if they include an occasional postmaster general at a chamber of commerce dinner—Mr. Wilson both “fought the air” and played “parlor socialist” the other night—and all these things must go outside the pale. We have reached the stage of social development where the social order must defend itself by finding pains and penalties for the crime of loose talk.—New York Press.

6-: parlor socialist and parlor revolutionist—from the Springfield Daily Republican (Springfield, Massachusetts) of Tuesday 8^th December 1896—here, parlor socialist and parlor revolutionist are used derogatorily:

Theodore Roosevelt writes to a New York paper in commendation of the work of the Legal Aid society of the metropolis as follows: “Any police commissioner sees so much misery and suffering, and grows to feel such impatient contempt for the way in which that misery and suffering are aggravated by the parlor socialist and parlor revolutionist of the Henry George and Bellamy stripe, that he feels a peculiar gratitude toward the men who really do work to make our civic conditions better and to raise those who are struggling with poverty and misfortune.”

7-: parlor socialist and beer-room socialist—from How Not to Better Social Conditions, by Theodore Roosevelt, published in The Review of Reviews. An International Magazine (New York City, New York) of January 1897—here, parlor socialist and beer-room socialist are used derogatorily:

Often the head in the air social reformers, because people of sane and wholesome minds will not favor their wild schemes, themselves decline to favor schemes for practical reform. For the last two years there has been an honest effort in New York to give the city good government, and to work intelligently for better social conditions, especially in the poorest quarters. We have cleaned the streets; we have broken the power of the ward boss and the saloon-keeper to work injustice; we have destroyed the most hideous of the tenement houses in which poor people are huddled like swine in a sty; we have made parks and play grounds for the children in the crowded quarters; in every possible way we have striven to make life easier and healthier, and to give man and woman a chance to do their best work; while at the same time we have warred steadily against the pauper-producing, maudlin philanthropy of the free soup kitchen and tramp lodging-house kind. In all this we have had practically no help from either the parlor socialists or the scarcely more noxious beer-room socialists who are always howling about the selfishness of the rich and their unwillingness to do anything for those who are less well off.

8-: parlour socialist and club socialist [cf. also 2 above]—from a letter published in Justice: The Organ of the Social Democracy (London, England) of Saturday 10^th April 1897—here, parlour socialist and club socialist are used derogatorily:

It is necessary, and should be the duty of each comrade to take up some work either in education, agitation, or organisation. But the something should be something useful to the Social-Democratic movement, and not a useless waste of time. It should not be the “boozing” of the club Socialist or the “slipper warming” of the parlour Socialist, but the active, determined, out-door propaganda of the real live Social-Democrat.