I think most men hate their butts because most mens' bums are crap.
Girls are much better at looking after our bums. Men just hope for the best.
At the gym I use, there's a machine called a Butt Blaster. It's great for giving your bum a serious workout - the sort where you can hardly walk afterwards.
But ... hardly any men use it. I think they see it a bit camp to concentrate on their arses.
jayne have you noticed when men are young there bums are taunt and sexy mostly, when they get in to there fifties and beyond there waist and bum merge together!!!!