But I don't quite understand your point. My point was that if your goal is to end racial discrimination, free-market forces left to themselves are not sufficient. Sometimes legislation is needed to level the playing field and make non-discriminatory businesses economically viable.
Does your post relate to that, and I am just missing something? Or are you heading in a different direction?
Your point - or at least the argument you justify it with - doesn't really make any sense.
Lets consider a result of the same argument applied somewhere different:
"...a significant number of people were environmentalists, and strongly favor clean air. If you opened a factory that polluted or purchased supplies from one, your customers would disappear. If your bank made loans to polluters who wanted to finance new machinery, your depositors would take their business elsewhere."
Suddenly your mechanism for enforcing racism seems implausible, right? After all, if it worked, virtually every popular left wing economic regulation would be superfluous.
But this ignores the historic reality of racial discrimination, which is that in some areas of the US, at some points in time, a significant number of white people were bigoted, and strongly (for no good reason) disliked black people. If you opened a restaurant that served people of all colors, your white customers would disappear. If your bank made loans to black people who wanted to buy homes in traditionally white neighborhoods, your white depositors would take their business elsewhere.
The civil rights laws of the 1960s made it economically feasible for businesses in these regions to stop discriminating; there were no longer any "white only" businesses for white bigots to patronize.
If you want to argue that in our more "enlightened" times, such anti-discrimination laws are no longer necessary, that's fine, but you will need to provide a certain amount of proof that things have changed.