
I don't think the OP's real life comparisons meant--let's take the samurai one for example--that only Japanese people can be samurai and no other races are allowed, or that Japanese people make for better samurai, etc. Rather, when people first come up with their character, they start with the idea of an archetype. Well, I guess I can't speak for others--that's how it usually works for me, at least. So when the idea "samurai!" pops into someone's head for a character, it seems a little... counter-intuitive, I guess is the best way to put it, to then make said samurai character a white guy, at least if it's for no reason more than "I prefer to play a white guy." In fact, I'd argue that where real life races are concerned, that can be seem just as (if not more) racist--to change the respective race of a member of some discipline that belongs to another culture, especially when whitewashing or changing from a minority to a majority--than to say "all samurai should be Japanese."