I don't think boxing is good therapy. I think boxing is a good way of channeling violence into a more socially acceptable form. Young men often need these kinds of outlets like sports, the military, or police work, or else they can become socially destructive individuals. However, I'm not sure that it always works as a catharsis. Most psychological studies show that viewing aggressive things or acting in aggressive manners actually reinforces feelings like rage. A better therapy for rage is like Benn said, watching Little House on the Prairie or petting a kitten. Smiling and laughing are better ways to release unwanted anxiety than punching things which in most cases just helps to amp people up.
Definitely an outlet for rage in Benn's case, you can see that in the way he fought, he came to take his opponent's head off. I don't think it's true for every fighter though.
a good therapy for rage is to manipulate your submodalities and completely relax your muscles, you cannot feel the emotion of anger if you completely relax your muscles.
