Is my communist friend naive or what?

I think that in the long run, personal gain cannot exist unless it goes together with the collective interest. This is because personal interest cannot thrive in an environment that will not be supported by the collective. For example, say one can profit significantly from manufacturing products, but to maximize profits for ones interest, they pollute the environment. The collective want a clean environment to live in. As a result, in the long run, the self-interested person polluting the environment can no longer manufacture goods at a significant profit because the collective will no longer be interested in purchasing that product. As a result, the self-interested person must align their goals with that of the collective in order to regain profitability.