Judging an individual by membership of categories always introduces bias. Even if Mexican restaurants are for some reason worse on average, say 9/10 are bad, then assuming that a particular restaurant is bad because it's Mexican is biased. Sure, there's a 9/10 chance that it's bad, but it's unfair to treat it as bad without any other evidence.
Insurance companies do this sort of thing all the time.
Insurance companies do this sort of thing all the time.