Baldric - // Ah, the SO Rule,
//what would you call that ?//
Shrewd Business Practice if they had not seen me before,
but under those circumstances, I would be looking for somewhere else to eat, not getting wound up about. //
I believe you are missing the point here.
Asking unknown customers to pay in advance can be construed as shrewd business practice.
Asking some customers to pay on the basis that they are black, with the unspoken inference that they are more likely to skip without paying is not shrewd business practice, it is racism, and it's against the law.
If people don't get 'wound up' about being treated illegally, then laws are not enforced, and society suffers as a result.