Ras, there is a difference between racial prejudice and institutional racism as a social and economic system. There is ample evidence that the latter is largely influenced by class and economic exploitation.
But the fact is a little 'natural prejudice' was already there. I would agree with that when the Europeans started enslaving Africans the effects were amplified and it became institutionalized racism.
For instance, in colonial Southern America, there were no racial segregation laws or laws prohibiting teaching Black people until Bacon's Rebellion, when slaves and white indentured servants rose up together-- after that, White landholders were determined to never let that happen again and set up a legal and social system to prevent poor Whites ever getting on with Black slaves again.
There is nothing odd about different people interacting beneficially together when both face an immediate danger, in this case, the rich White landowners.
So while it may be true that racism would exist independent of class and economic conditions, it seems pretty obvious that it is exacerbated by class and economic conditions, and that many institutional forms of racism would not exist without an economic or class power interest being involved.
I never denied that things likes like economics could amplify those sentiments, my point is that they are amplifying things that are already there. Again let me remind to that these differences have little to do with the colour of one's skin