He needs to get rid of people who call him a nerd.
Not our problem
stand up to them. Then torment them back. Don't get mad get even. If it comes down to it I would use deadly force. The way I look at it is it either me or them.
talk to the police about it
police are reactive not proactive. Basically police are report takers. They just keep a record of what happened
Well, there is this one method that's had some success in the past, but he's gotta have awfully strong legs...
Lol! It's just another "nerd-thigh strangling jock-bully" joke.
He needs to stand up for himself and fight back. He may not be big but with some practice he can easily learn to take down an opponent.
Start practicing some form of Martial Arts. It will help with self-esteem, confidence, physical strength and mental strenght.