In arguing against this conflation, Keynesians of some sort like to point out Keynes' explicit remarks on Marx:
"How can I accept a doctrine which sets up as its bible, above and beyond criticism, an obsolete text-book which I know to be not only scientifically erroneous but without interest or application for the modern world? How can I adopt a creed which, preferring the mud to the fish, exalts the boorish proletariat above the bourgeois and the intelligentsia who, with whatever faults, are the quality in life and surely carry the seeds of all human advancement? Even if we need a religion, how can we find it in the turbid rubbish of the red bookshop? It is hard for an educated, decent, intelligent son of Western Europe to find his ideals here, unless he has first suffered some strange and horrid process of conversion which has changed all his values." -- John Maynard Keynes, "A Short View of Russia" (1925) in Essays in PersuasionEqually of interest, perhaps, is the abuse that Soviet Russia heaped on Keynes.
The following are some of the first comments in Soviet literature about Keynes's General Theory:
"One should not say that the conclusions of Keynes are a novelty. Analogous repair patches on capitalism were offered by reformers of various creeds in the USA and other countries long ago. Economic reality has proved the unadaptability of all these prescriptions for the saving of the capitalist system a countless number of times..." -- L. Freiman, "Bezrabotitsa V Kapitalisticheskikh Stranakh", Planovoe Khozyaistvo (1938)
"This theory is one of the many attempts of bourgeois science to adapt its apologetics to demands of the rule of capital at the present stage of development." -- A. Arutinyan, "Garvardskie Ekonomisty I Burzhuaznoe Konyunturovedenie, Problemy Ekonomiki (1940)
"Through the right-wing socialists, Keynesian ideas penetrate the working class. Keynesianism sows among the workers the harmful illusion of the possibility of overcoming crises and unemployment within the framework of capitalist society. The fight against Keynesianism is one of the most important tasks of the ideological work of Marxist economic science." -- I. G. Blyumin, from the Introduction to the first (1948) translation of The General Theory of Employment, Interest and MoneyHere are some extracts from a thesis accepted by the Institute of Economics of the Academy of Sciences of the USSR:
"The chatter of the possibility of liquidating unemployment and economic crises in capitalism serves Keynes only as a smoke screen with the help of which he attempts to hide the real content of his especially anti-people's program directed pointedly against the working class. The unmasking of the conscious distortions by Keynes of the role of the contemporary bourgeois state is the most important requisite in explaining the real content of the Keynesian program of the transition to the so-called 'regulated' capitalism, which in itself is nothing other than a new charlatan project for the notorious 'organized capitalism'...
...The socialist system of the Soviet Union is the best refutation of all the Keynesian apologetics of capitalism and is proof that the only method of liquidating crises, unemployment, and all the other inevitable fellow travelers of capitalism is the destruction of the latter." -- V. S. Volodin (1950)
The above abuse was compiled and translated from the russian by Carl B. Turner (An Analysis of Soviet Views on John Maynard Keynes, Duke University Press, 1969).
This story about the antipathy between Keynes and Marxists is complicated by the existence of Michal Kalecki and of Paul Baran and Paul Sweezy.