Rap music doesn't glorify anything. It just shows the things that are common to so many people's lives.
And video games. Violent video games to be specific. Are only a result of tradition. Plus the violence is usually constrained to a certain area. Most people who enjoy "war-games" know exactly how crap real war can get, they'd be the first to fight against war. A game is enjoyable precisely because it is unrealistic and no one wants realistic games.

Videogames(in general this time) might be responsible for violence though. In an indirect manner. Often people play video games to get away from the real world. This at the same time sterilizes any thought they might have of acting against violence.
Video games are partly escapism. A balance is required.