Grand Theft Auto V's Trevor picks on social groups, rednecks, gang bangers, military personnel, and hipsters, and when he does so, he takes offense at one or two members of that social group before he then allows his rage to explode into a kind of murderous generalization. If one hipster offends, then kill them all.
Competitive gaming is about power, hierarchy, leader boards, and all the ways of establishing a pecking order among players. Owning someone is the goal in online gaming. It's about making someone your bitch.
The purely sociopathic Grand Theft Auto player just seems like another character in a narrative designed to critique the game's shortcomings as a game, more a straw man than any real player that I know (or am).
Rockstar may have just borrowed a bit of The Wire's approach to telling the tale of an American landscape for the sake of painting the portrait of America that Grand Theft Auto has always been interested in realizing.