How is discrimination the right side of anything (whether you agree with their cause or not)?
If they discriminated against gun owners because our weapons go against their religion, you'd be picketing them and calling everyone you knew to complain about it.
What's that poem about "no one was there when they came for me"?
Well, first of all, You can be discriminated against. By ANYONE except the government as long as it does not infringe on areas that the government has mandated as theirs to control (Heart of Atlanta Motel v. United States, note the reasoning on how they ruled)
Why as a business owner should you not be allowed to give services to those who you do not wish to? This is exactly the point that you made in your comment, what if someone (the government) came in and told the owner of a business (a church that owns a school) that they have to capitulate and go against their religious beliefs and allow people (person's that offend the very basis of their moral values) to stay and be served by the business owner? That would be a Constitutional violation. There is nothing in the Constitution that says that you must provide something for anyone, as a matter of fact there IS something in the Constitution about not having to work for someone when you don't want too. (Hint: we fought a war over it)
I am discriminated against all the time by companies that don't like my gun. Ever go to a mall? it is probably owned by Simon, and if I recall, they have a NO gun policy in their malls. (Not like it stops gangbangers) But everytime you go to a mall they have the right to ask you to not be armed or not come onto their property. It is also a property rights issue. And remarkably, no one seems to be bothered by it enough to picket.
I defend everyone's right to be what ever they choose, (within the confines of the law) but no one person's percived right should trump another's to be free from another. (there is a SCOTUS case that something like that was said concerning privacy)
This is also a private school, ie private business. Public schools cannot do this and nor do I think they should be allowed. Or if they accept federal money. But in my opinion an Aryan Nations school should be allowed (If not tax dollars go for the funding) to prevent anyone they want or don't to attend their school.
Aryans (as dumb as I think they are) have the same Constitutional rights that I do. If I don't protect theirs to be free from interference, I can expect the government to interfere in my private life too.
(Disclaimer: I am not advocating bigotry in any way shape or form. I am advocating a private business being able to not serve those they don't want to.)