I know alot of people who like football me included, and let's face it football is violent. I know a lot of people who like to hunt, and that's violent (for a good cause mind you). Kids play tag somewhat violent, dodge ball essentially throwing a non-lethal projectile at another human for sport. Society from yesteryears and now has always been violent just in different ways it seems less so back than but not really. Virtually killing someone in a video game is no less violent than virtually killing someone in a paintball arena.
As someone who has played and completed GTA 5 and is quite fond of the series as a whole I can tell you the level of violence depends largely on the player. Sure you can go running around murdering everything in site and banging ladies of the night. Or you can play the game like I did, like a scarface, godfather, or heat movie. Kill as few cops as you can get away with as much cash as you can and move up the criminal world.
It is really annoying to me when people accept one version of unjustifiable murder in the form of a martin Scorsese film, but when it's a video game it's trash. It strikes me as a bit pretentious.