There was a podcast called invisibilia and the first episode talked about a guy with a similar issue of violent intrusive thoughts. One explanation they gave was that he was more caring and empathetic than most people which is why it affected him more. It won’t “fix” your thoughts, but might give you more information.

Regarding the class, slumberkitty had good advice. Tell the school you want to walk or you want a different rotation. Don’t just say “I don’t want to do this”. They’re not dumb and will understand without you having to explain. However, they might ask questions to make sure that you’re not in trouble currently and there isn’t anything wrong with the class. If that’s the case, be confident and say what you said in your message “I think the class is important for my peers to know, but I don’t feel comfortable”