Do you think I should beat up my boyfriend's friend?
Why do you want to hurt him?
I'm tired of listening to him badmouthing my boyfriend.
That would be a bad thing for you to do. It's wrong to hurt someone physically. Maybe you should bring it up to your boyfriend so he can talk to his friend instead of getting involved.
I trust my boyfriend, he's not going to fix this.
It's still a bad idea to beat somebody up. If he's seriously hurting your boyfriend, maybe you should get some authorities involved instead of taking it into your own hands.