he won't like it but you have to be firm--- set a time limit and don't let him play any games with (M)ature ratings for sure.....
send him outside
SERIOUS martial arts training- will keep him interested in the protection of others and self defense- Get him in a karate school that teachers mottos that instill self discipline- fighting is DISCOURAGED- but a warrior mentality of protecting the innocent is encouraged. So this is not just physical, it teaches emotional and ethical integrity if you get in a good school---- so ask around- My son teaches Kung Fu. My husband is a classical Okinawan instructor, it's all considered martial arts but like I said the fundamental teachings need to address morality and a sense of pride from NOT using the skills- only learning them to use to defend yourself and family.
The cost is minimal when you consider they truly get some real life training/
Perhaps unplug the computer.