For 'bitching', read talking. That's just a derogatory male term for women talking (see also 'gossiping'). So, why do women talk and men fight? Because men aren't as emotionally or linguistically sophisticated as women. Women have always had to talk their way out of things - they aren't as physically stong as men. Men have the luxury of being able to fight if they want and not worry about the delicacies of conversation of discussion. Men often like to think this is a primitive, Neanderthal 'instinct'. It probably is.