We have also done as many ugly things to one another in order to build cross-national entities, like empires and communist-based internationalist mega-states.

>I don't think we should sweep racism and xenophobia under the rug with the argument that "boys will be boys"

Well, first let's not call the desire to maintain one's national identity "xenophobia", the same way wanting to have your own house and family, and live as you like there, and accept whoever you like, is not "strangerophobia".

You think previous empires were built because they were more concerned with equality and anti-tribalism?

"Melting-pot entities" are concerned with the same things ("strategic control of resources and geo-political regions") too. Cross-national melting is mostly about whether you allow the peoples you control to keep their identities or you want to abolish them too, for less market friction and/or smoother political control. USSR comes to mind on the latter. UK/US/EU on the former.

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.