Sigmund Freud said that the reason we love punching others and hurting others is that our Id (the dark side of us that controls our instinctual wants and needs) likes the feeling of punching someone because this type of stimulus is pleasurable to it...Our Id instinctually wants to derive pleasure from our most basic and primitive needs...sex is one...food is another...violence is the third...the Id doesn't care about morality or what is good or bad...it just knows that it wants pleasure...This is why the Id needs the Ego (our consciousness) to keep it in check...for example, the Id sees a beautiful girl with a bikini on and the Id say's "WOW!!!!...I want that right now..I don't care how I get it, I just want it...go ahead and rape her"! the Ego says "well I can't do that or else I will wind up in jail for a billion years"!...so then the person, instead or raping her, delays gratification and moves on until such time that this sexual need can be fulfilled...the theory goes that thosae who engage in constant violence or raping have weak egos which are not strong enough to stand up to the instinctual wants of the Id which are very very powerful drives which humans have had for thousands of years...this explains why punching someone feels so good..it actually is pleasurable to a certain aspect of our personality