1. You are right, I am repeating myself. Sorry about that. And to reply with the historical evidence and documentation of the relation of the rise and reproduction of capitalism and slavery and racism would be to repeat myself from earlier posts and to summarize a fairly well known body of literature, much firmly within a marxian tradition. So I will give everyone a break and pass, but I would be glad to forward references offlist if you like, because you may not have been subscribed to lbo when this discussion took place.
2. My 'thought experiment' was in response to your own similar statement about capitalism continuing on without racism. So either both of our thought experiments are valid or neither are.
3. I don't think Marx was reductionist or mechanistic, but a lot of marxism has been.
4. Racism and the concept of "race" are not the same thing. We could also follow Oliver Cox (Caste, Class, and Race) and distinguish between racism and what he calls race antagonism, where the former is ideology and the latter describes 'real' social relations. I don't make this kind of sharp distinction between "ideology" and "reality" but perhaps this might help? To go into this more would be repeating myself, but suffice it to say that I do not believe RACISM is an "illusion."
5. I don't subscribe to your epistemological position regarding "testability" or "verifiability." But history is crucial, and again, if you want references or a summary of the historical evidence off-list I would be happy to provide it.
Thanks for the conversation.