[kahljorn]

"If different groups of humans cannot morally judge the actions of other groups of humans, then how can the same moral rules apply to all humans? And if there is no morality that can apply to all humans, then doesn't that kind of undermine all the ideas of human equality? Why should we recognize different groups of humans if these different groups cannot recognize the rightness or wrongness of eachothers' behavior?"

I read your post and found it to be interesting, big papa goat. The only thing I can imagine telling you as a solution is that morals are incredibly relativistic(as you've noted), and the only way to build a good moral system is objectively, they can have nothing to do with the human situation itself.
Nobody really wants human equality, every race/nation (anything, really) wants to feel better than every other nation. We even have that kind of competition on these message boards.
As to your last question, maybe we shouldn't. They really aren't different, they suffer from the same anxiety as everybody else, and the same desire for their beliefs to be right(and their beliefs were all likely forged in similar situations). These are innate feelings every human being feels, a sort of an identity crisis.