Yes, the movie-makers of today are pushing it, and yes, it is grisly. This is surely not a scary movie. Of course you wouldn't let your 12 year old watch it, but older teens mature at a variety of ages, some much quicker than others. Why must we lump every teen into the same category, and deny them their maturity? I love horror movies, and that is to no fault of my parents, for I snuck them for quite some time. It's not like I didn't get punished for it. There is violence that is obviously fake and overdramatized, and there is drug-abuse, and self-mutilation. Who is to say that these things don't already happen? Who is to say that having a teen see these things isn't going to benefit them, when they see the consequences of what the drugs, etc. lead to? You call it desensitization, I call it an awareness of the world around us and how screwed up it has gotten. People in our history books have done much worse than this man, and I don't see you complaining about them.
Besides, he tells you to appreciate your life. Minus the deaths, it is a good message to live by.