[totally offtopic] That's ridiculous. Taking the Montgomery, AL bus system as an example, black customers were critically important to the economics of the city transit system, which is one reason the Rosa Parks bus boycott was such a big deal. Outside Montgomery, we do know of streetcar companies who refused to segregate their customers, until they were forced to do so by the government (See Roback, Jennifer (1986). "The Political Economy of Segregation: The Case of Segregated Streetcars". Journal of Economic History 56 (4): 893–917. doi:10.1017/S0022050700050634).

Racial segregation in the U.S. South was a wholly political decision - in fact, it was politically pushed by pro-white Democrat politicians in opposition to the Republican party (which used to be pro-integration).

More like "the legal system backed up the whatever impressions those in power, i.e., whites had".