I can agree this game is rather questionable, but at times ESRB (TM) goes a little too far with their ratings. This game is not as bad as it is rated.
No Sexual Referenes whatesoever
Violence: yes, of course you can shoot and stab, but not the shooting and stabbing is not like that of say....GTA? Most are concerned about a new feature in the game, the knife. But the knife was not put there for pure killing, but it is used as an extra help for stealth, which is the opposite of non-violence. For example, instead of using the knife to stab the guard guarding the door, you can use it to open up a circuit box and bypass it so that the lights go off and you simply go around the guard. No bloodshed, not even the boring "elbow" from the first installment in the game. To make this point even more proven, the game penalizes you for killing soldiers or civilians.
Also, the game has a pretty good education value to come with it. I was amazed when i recently played the game, and it was like watching the news. The game doesnt have the boring plot like: "gang tries to take over the world" or "nuclear bomb....stop it". The game backs up its plot with actual events happening today.
All in all, this game is appropriate for those my age but are also critical thinkers. When I played the game, it got me interested in current events happening today. Not for those who are for pure blood.