I'm was going to tell my creepy friend that I would go to homecoming with him, but then I changed my mind
What is the reason for changing your mind?
I would rather spend my time doing something else.
It's usually frowned upon to go back on one's word like that.  However, if you feel uncomfortable about going out with your friend, it's okay for you to want to avoid that kind of situation.
He is butthurt because we won't go out.
Next time try to prevent a situation like this. If you are going ayways you might find out he isn't actually a creep anyways.