You may start an 'arms war' with the child. Perhaps he has also learned about streaming, where a video downloaded to the PC can be watched on the 360. Even a cheap laptop in his room can hold ANY video he downloaded or converted, then the 360 can attach to a server (TVersity, maybe) running on it.
Or a few MP4 videos stored on a USB stick and carefully hidden from Mom and Dad.
If I wanted to prevent all this, I'd threaten to move the 360 into a trash can, then DO it next time there's trouble. However, I was the kid who used to turn the TV antenna at night so Canadian TV stations with naked women and more came in clearer, so what do *I* know?...