Sure, I agree with that. Individuals choosing products of socialist production will not bring about socialism. However, as I should probably note more often, individual choice does help shape social institutions. It's like your response to people about voting: given the choice between a moderate D and a batshit crazy R, it's reasonable to vote for the D, even though it certainly won't bring about socialism. And just so with supporting co-ops, credit unions, public schools, and open source software.
Miles