But, wow! How do all these magicians get into fights? I hardly ever have come across hecklers like that, even when I was in school.
Some people just don't want to see a performance. Play it safe and stay away from violent hecklers. It is very tempting, but do not beat up hecklers. The media and police do not like it. Imagine if a great performer like Copperfield, Blaine, or any other famous one beat up a heckler that embarassed them. The media would swarm them, and they would be pressed with criminal charges!
The only time it is appropriate to attack a heckler, in my opinion, is when he is attacking you. That is where security and self-defense training comes in handy.
Now, if he just grabs your wrist: If he is hurting you, obviously you have to defend yourself, but if you can just ask him to let go, do that. If he does not let go after asking, there are simple karate moves out there to free yourself from him and send a harmless message to not do that.
The best method though, is to always avoid fights! After that is just self-defense.