If they haven’t made a public statement that they’ve stopped excluding atheists, why should anyone assume they’ve changed their policies?

Sounds more like Dig’em than Froot Loops to me.

The principal doesn’t give a shit about the dress code beyond how it can provide a way to hurt black students. In that context it becomes obvious that they’re going to extreme lengths because they consider inflicting harm to be important.

Is being an open nazi and rallying for hate speech legal?

Yes. Any law making that illegal would be unconstitutional. They’re assholes, but until they do or say something that is part of commiting a crime they still have a right to free speech.

Not since they started forcing minors to work on it.

It doesn’t sound like he’s been convicted of a crime yet…