I don't love my stepdad
Is there a reason why you don't love him?
He's stupid and he's always offensive
Just because someone is family doesn't mean that you have to love them. You don't have to love someone just because you have a relation to them.
At the end of the day, I just wish he would leave. I'd be much happier if he just died or something.
Not loving him is fine when you have reasons for it but you shouldn't wish that he would die. It's wrong to wish something that bad on someone and I'm sure that's not how you actually feel. Try to just stick to not liking someone instead of expressing that in such an extreme way.