I am pretty sure different versions of Call Of Duty have different age ratings. Turning off the extreme violence/gore etc is easy to do if you won't but it is still an intense game with lots and lots of first person violence. The gameplay is very intense and mature and may be 'too much' for younger teens. It is not just the violence and language that is not suitable.
DS and I have chatted again today. I explained that he needs to be able to distinguish reality from the virtual world and that is more important for him than some of his friends. If he does go into the army then in a couple of years he will be training for real.
I think that yesterday was a bit of a glitch, he was tired and had got himself worked into a state. By the end of the evening he had put his games controller down and picked up a guitar and seemed a lot happier in himself.
No GTA allowed here and DS1 is 17. Mine both had COD at 14 and so did their friends. I know this because I checked. Console in the living room though. I have no problem with the game, doesn't appeal to me but it seems to let them socialise and let off steam.
My DS 13 ordered COD on his own Amazon account I hit the roof when it was delivered and confiscated it. Waste of £25 there and a whipped puppy too.
But... I then researched it in slow time, consulted with some RL friends, and had long talk with DS. He was eventually allowed to use the game, with supervision at first, and with the "gore" turned off. I watched for a few sessions until I fell asleep and he got bored very quickly.
Good lesson for us on communication and boundaries. Not sure it helps you?