It really bothers me when really nice guys turn jerk because of one girl. This one guy I know was sweet, modest, confident and had beautiful dreams for himself.
  However, this girl he went out with dumped him, got back together with him then cheated on him. Now he's an asshole to women (well, except me of course), he treats them the way his ex-girlfriend treated him. He gets with them, uses them and leave them. His confidence turned cockiness and his dreams... not so beautiful anymore. 
  He knows, not all women are the same because I show him that every time we hang out. The thing is he's not willing to risk it. 
Clearly, women do their fairshare of "dogging". Im pretty sure he'll eventually heal, find an amazing woman, have a daughter, be apologetic towards the women he wrong and be at peace. 

I am by no means saying that what he's doing is justifiable. No, two wrongs don't make a right, but can you blame him? One bad apple ruined it for the bunch.