A stupid asshole concerned with stupid shit, hense douch bag. Someone who is so concerned with themselves, so much so, that they don't see they don't just undermine everyone else, but themselves as well.
That douch bag at the club with all the bling around his neck and sporting the newest fad kept making creepy passes all night. He does not see the girls all left and he screwed all the other guys’ including himself.
That slutty girl at the club has two kids and a husband at home and would rather shake her ass, what a douch bag. She does not see her kids will grow up to hate her and her husband will eventually leave her.
A douch bag professional athlete snubs and/or insults fans. He does not see that he is screwing over his fellow athletes, his fans, and eventually himself.
A successful business man fusses over his car, his suit, clothes, house, and/or jewellery. The doch bag cares nothing for his children, his wife, his community, or people at work. Then he has the balls to complain his wife cheats, his kids are losers, his car continually gets vandalized, and everyone at work is trying to get him fired.