Well, here's the thing. If his parents are going to sit down and explain the mature themes to him, then that's one thing. But, what is the likelihood of that happening? I don't mean to pass judgment, but I'm going to say that it's slim to none.
From what I’ve seen spending time in shops and from frequently talking to a friend who used to run her own game shop, less than 10% of parents will show any concern over the content of a game. The woman who ran the shop is a mother of two kids, both under 15 and would watch very carefully what they played. She’d do her research on what they’d play. Halo was fine but games like GTA and Manhunt were off limits to them. She’d refuse to sell M games to anyone underage without a parent present and would frequently get parents coming in pissed that their kid couldn’t buy an M rated game on their own, forcing the parent to be inconvenienced into take part in their child’s life. Never would the parents care about the content, just that they got stuck going to a game store to get whatever the game was.
It’d be nice to see parents give a shit about what they expose their kids to and at least take the time to analyze the content and explain it so the kid gets a chance at coming out with a clear perspective of right or wrong. Most kids are just left to figure it out on good faith that they know better.