Would you find it acceptable that those kind of people teach it in your schools? Or here's a question that sort of relates to the issue but on a more contemporary level, how does this relate to the issue of cyber bullying? Your child is getting vicious texts from someone that are threatening his life/happiness/safety.....is this 'acceptable' because of the requirement of freedom of speech? Can you impinge on that awful persons right to say what he is saying? What if he's hanging posters around the neighbourhood to the same effect that are causing your child untold distress? Are there any moral/ethical limits to this 'free speech'?
I don't think any of those people are going to be hired as teachers in our schools to teach subjects like that. But, I think in colleges, if a teacher has an opinion on something that they wish to share with the class, it is permitted to provoke some thought on the topic. I think that a professor made some statements that were not favorable to America and its government, and there was some controversy about that, not sure what the result was, it was a long time ago.
If my child was personally getting vicious texts from someone threatening his safety or his life, it would be a criminal matter for sure. I also think it's the parents obligation to teach their children right from wrong, so that if they see or hear any Nazi related talk or Satanic propaganda, they will take it for what it's worth and not let it affect their personal lives.