No, it was because white people would refuse to share busses and schools with blacks. The free market responded by giving what most of its customers demanded.
I don't believe you but I'll accept it as true for the sake of argument. Even assuming that's true, it doesn't matter. No business is required to give you service. You don't get to point a gun at someone and say "let me be a customer", no matter how desperately you need that good or service and no matter how arbitrary the reason for being denied service. I think it sucks that some businesses are operated by racists but that doesn't give you the right to use violence. The use of violence is justified in immediate self-defense only.