How about I tell my girlfriend not to let a guy walk her?
Are you kidding? Why would you tell her not to walk with him?
I think he's a pedophile that could become a danger to my girlfriend
You shouldn't control while in a relationship. Do you have proof he is dangerous or are you being paranoid?
I am mad and I am going to my girlfriend's parents house. I'll teach him a lesson
Stop. You could get in serious trouble for hurting him. It would be better to talk to your girlfriend about the danger instead of trying to control her or hurt him.