I was friends with a guy for a while and we really don't fight too often except when his mentally ill nephew is around and hanging with us cause he has no one else to hang with.  My issue with him is that he has a thing with being sexually inappropriate with girls that he somewhat has crushes on and has gotten in trouble for inappropriately touching women in public.  So much so that my younger sister tries to keep her distance from him.  My friend constantly defends him for his actions and says he doesn't know any better and doesn't know how to appropriately handle his loneliness, only for me to reply with he better not lay a hand on my sister or else.  Well, his nephew finally crossed the line when he supposedly accidentally felt up my sis when he supposedly bumped up against her.  She felt violated and I confronted him about it only for my friend to get between us.  And like everytime, he defended his actions and I told him I can't have my sis around him any more, which he did not take too well.  He accuses me to singling his nephew out in public, making a scene and bullying him, which pissed me off to the point that I told him to F off and even went as far as threaten his nephew that if he ever gets near her again, I'd kill him.  Did I overreact or was I right to be worried.