What age are you?
And to be honest it's not the violence that would stop me letting kids play this but the language, everything is used in this game and I mean everything. You hear it when out on the street, standing still, in missions, in the taxi, basically all over. The violence isn't that much and frankly it's as violent as YOU make it. You can shoot everything that moves but unlike previous GTA's, the police etc will not be easy to escape if you do as they are very ruthless and when SWAT and beyond arrive they are accurate and constant and will take you out.
Remember there is prostitutes, drinking, drugs, guns, killing etc so this game is not for the young uns, sure you can say that you won't be bothered by it and last time I checked despite the 10 years of GTA (man the first was great!) noone as far as I know has Rocket Launched a bus (though you can't lie and say you've never thought about it jokingly).
I would say 15 and up would be (hopefully) mature for it, and as for gore that's not the core component, the core aspect is that it is you playing as Niko that does all of the actions onscreen. Anyone who can't make the distinction between fantasy and reality has a screw loose anyway and would snap with a tv show (Dexter?), Movie (Clockwork Orange, Scarface etc?) so to say the game might make you a psycho is complete rubbish, but the content of the game does warrant the rating.