[katiuska]

It depends on what you mean by bigotry. Humans are inherently categorical--human instinct isn't as simple as a direct stimulus and response, we create categories because we need them to tell us how to react to things. The tendency to create categories of "us" vs. "them" is unfortunately deeply held and possibly a habit developed out of years of tribalism (but not one that is impossible to overcome). If you mean specific beliefs, or more general feelings depending on, say, sexuality or amounts of melanin in the skin, that's definitely learned. There is no gay-hating gene.