The reason he was (finally) banned from Twitter was for encouraging his racist supporters to harass Leslie Jones and send her gorilla memes (a wildly racist trope, as you know).

So yes, he's racist.

Proof? I've always heard it insinuated that the instructured his followers to send her gorilla memes but the only thing I've seen Milo say about Leslie Jones was that she looks like a former male sex partner of Milo's.

Given that there is such a high correlation between religion, race and cultural background I don't think it's always possible to say that racism is fine but bigotry and xenophobia aren't.

They are all inextricably linked.

We need to be able to criticize cultures, as they are choices and not unchangeable traits at birth, and some cultural behaviors are absolutely unhealthy. Your premise opens up certain cultures to be immune to criticism, which is a terrible thing.

You choose your beliefs. Not your genes. That's the problem with racism. Genes are not a thing you can hold someone accountable for.

In America, there isn't really. For the most part, immigrant groups have adopted a culture completely or substantially different than the one from which their ancestors came.

So that whole pedophilia thing is ok?

"Some of those relationships between younger boys and older men, the sort of coming of age relationships, the relationships in which those older men help those young boys to discover who they are, and give them security and safety and provide them with love and a reliable and sort of a rock where they can’t speak to their parents."

-Milo Yiannopoulos

He's married to a black man...

If someone is married to a woman they can't be a misogynist?

Can an anti-Semite marry a Jewish person? Can a black supremacist marry a white person?

Yes to both

then how serious is their hatred?

That doesn't make him not racist. If it means anything at all, it's that he's a hypocrite as well.

All the responses to you below that fail to give you any examples let's you know all you need to know