Yes, Grand Theft Auto V glorifies violence, because it basically teaches people how to commit violence. Grand Theft Auto V is a whole game where you do nothing but go around and steal cars. It is a fiction to think that a person can look at that all day and not have it rub off on their mind.
It is very clear that Grand Theft Auto V glorifies violence, pretty much all of the Grand Theft Auto games have glorified violence. The game is correctly marked as an adult game, however, and it is fine to have games that demonstrate such violence. While it may not leave the best impression on young adults, it can be used as a tool to demonstrate the difference between games and real life.