Okay, I guess I'll wade in a bit

Just a few thoughts:
1.) Suppose you live in a border city where white people make up 12% of the population. Suppose there is historic tendency of the majority race in your city to prefer to do business with "their kind". Suppose in your lifetime there was a time when you were forbidden from even entering their businesses? Would you think that he potential for some sort of lingering bias in some is unthinkable? Do you think you would feel an obligation to do business with the white owned businesses when possible?
2.) Many black owned businesses are in communities where other people don't feel as comfortable coming. Honestly, in many cases people don't feel as comfortable for good reason. But either way the end result is that they are in communities where others do not or will not come. In those cases, if the black community does not patronize their business, no one will. For example, our church happens to be in such a neighborhood and I know this to be a reality for some of the business owners around.
I'm just throwing these out for your consideration. I am not a proponent of racism anywhere by anyone. I'm just wanting to expand the scope of this conversation.