How did I get banned for a Screenshot?

You really don't think your opinion matters? The whole point of posting on here to state your opinion otherwise you'd just be a drone. Regardless of that I do understand that my screenshot, which I did not post by the way, violated the Terms of Conditions.
What I don't get is how everyone else that posts in M rated games isn't banned. It says you can't post "extreme violence" which is in every single M rated game. That's usually what makes them M to begin with.

Also try naming one thing (other than a wall or a floor) in an M rated game that you could take a screenshot/gameclip of that would be rated E.

It doesn't matter what I think. It matters what the TOU and COC say. Willfully taking the pic and posting it is what got you got you banned. The game didn't take the screenshot and post it, you did. You got banned for it. What part of that don't you follow?

I'm not sure I follow along with your argument. Do you really think that a pixelated naked photo is worse than someone getting chainsawed in half with blood flying everywhere while they'rescreaming(Gears of War)? And you know I didn't edit the photo at all
its a part of the game that everyone sees you literally can't miss it because it's one of the objectives in the main story. Every screenshot and game clip on xbox live is auto uploaded. Usually within half an hour you'll see it show up on your friends feed
you don't manually upload everything.

Posting nudity will get you banned. This wasn't some auto posted video. You CHOSE to post it. Stop acting like it is the same thing.

What you are missing here is the single player game is rated M. The interaction on Xbox Live is not rated at all and every game explicitly says that in it's ratings box. Auto posting video is allowed by the game publisher and Xbox Live. Taking video or snapshots
and editing them and posting nudity, or video with swearing opens you up to being banned.

I suggest reading the Code of Conduct and Terms of Use if you are confused about any of this.