Cohen believes something quite odd, namely that "selfishness, and, too, our equanimity about it, are precipitates of centuries of capitalist civilization. (First capitalism destroys community. Then its defenders say that material incentives are necessary because communal ones aren't powerful enough.)" (178-9n)
But "selfishness" is an elemental property of the human will. It "belongs to man to do everything for an end," St. Thomas states; "the object of the will is the end and the good. Therefore all human actions must be for an end." (ST, II-I, 1, 1) It is human nature to seek happiness, and happiness is sought in acquiring and enjoying goods that suit each individual's nature and personality. Cohen is denying people their due, the fulfillment of a capacity that belongs to them by their very essence, and that is unjust. The search for happiness is not an effect of capitalism; it is a process which is best served by capitalism.
It is true further that capitalism de-communizes society, as in frees each individual from social pressures. Far from reversing this process as Cohen apparently desires, we must complete it. "It will require many long years of self-education until the subject can turn himself into the citizen," says Mises. "A free man must be able to endure it when his fellow men act and live otherwise than he considers proper. He must free himself from the habit, just as soon as something does not please him, of calling for the police." (Liberalism, 55)