Earlier quoted context omitted.
Yes, tribalism is human nature, and we have done very many ugly things to one another because of it. Much of modern advancement in civil liberties and human rights have come about because of the recognition that human nature is flawed and we need to act to fight our worse instincts. I don't think we should sweep racism and xenophobia under the rug with the argument that "boys will be boys"
What is racist about not wanting things to change? This is a totally separate issue from racism. Calling it "boys will be boys" or "girls will be girls" is a gross oversimplification.
You can justify anything by explaining away people'a xenophobia or bigotry by saying they didn't want change.
We just went through the same argument with gay marriage with people alleging great harm and the need to discriminate against gay people, causing greater harm to them.
I find great irony that people on HN who probably subscribe to ideas of dynamism and creative destruction and disruption as the life blood of innovation are defending cultural conservatism.