Why not quote VI Lenin, from State and Revolution?

Freedom in capitalist society always remains about the same as it was in the ancient Greek republics: freedom for the slave-owners.

The poverty of the working class was always the 'refutation' of capitalism. That's what Marx and Engels were concerned with anyway; their definition of capitalism is an economic system where a class of investors makes their living by siphoning off the value of other peoples' work, and therefore the division into a wealthy class and a class of wage-slaves, people who are forced to work at degrading labor in order to merely survive. Political power is severely diminished for this class, if it exists at all.

I don't know if there was a particular meme among Soviet people like it is among Americans. But at least to Lenin, I can say for sure that wage-slavery was his concern. Soviets interested in politics would certainly be quoting Lenin.

Not quite a refutation of capitalism so much as American society more generally, but the Soviets were found of pointing out the entrenched racism of American society to the point that "And at your place, they are lynching Negroes" became a meme/punch line in Soviet humor. As a punch line, it mocked that this was the only real response that Soviets had for anything. For example, look at this joke from 1962 (quoted on the Wikipedia page):

An American and a Soviet car salesman argue which country makes better cars. Finally, the American asks: "How many decades does it take an average Soviet man to earn enough money to buy a Soviet car?" After a thoughtful pause, the Soviet replies: "And you are lynching Negroes!"

Wikipedia cites equivalents in Czech, Hungarian, Polish, and Romanian, suggesting that this was common in the whole Bloc, not just the USSR. The punchline mocks the stance of the communists, but it also certainly indicates that this a common enough stance to be mocked.

Interestingly, there's compelling evidence that this line of criticism was potent enough to affect American policy. Most obviously, with the desegregation of the U.S. armed forces in the 1948, but there's evidence for a much broader effect on civil rights (I haven't read that book yet, however). That it would be an effective critique that the U.S. would feel compelled to respond to is quite understandable, of course, since the main fronts for Soviet and American propaganda during the 50's-70's were in the newly decolonized world (as well as Latin America) where White supremacism didn't have the same appeal as theoretical equality.

edit: Here are some examples of Soviet propaganda posters emphasizing cross-cultural/cross-racial harmony. Here's a particularly powerful one indicting American society by combining the torch of liberty with a burning cross, the statue of liberty with klansmen.