I would not care how non-racist a person may actually be in real life, if they choose to play a racist character, I will be very not cool with that
Does it extend to games set in historical settings? For example, are you expecting your Roman Senator PCs to at least pay lip service to the idea that they can do the many evil-for-us things that were basically expected of them (depending, of course, of the familiarity of players at the table with the era)? Or would you want the PCs to hold dear values? (and if I start a dedicated thread, do you mind being quoted there?) And if the players deviate too much, would you make them face the social consequences of it?