they are hurting them, as much, as the seconds hand sale of used cars is hurting car industry... it creates more new car sales... fighting this is the most stupid and ridiculous idea ever...
This assumption is only true if people sell their games to stores, and then buy new copies of the game.
Having worked in game stores, second hand game sales make a killing. And we'd happily buy back that used copy of the game, for some guy to buy a used copy of another new game that just came out.