I also have a son who's a gamer. it's a tighter community Than what you mentioned (Music or Religion) and way more exposure. Its not uncommon for him to spend 30+ hrs a week in his "community"
The upside is that there are more video game players on average than video game players who do something violent. But it’s helpful to keep people aware of cult-like behaviors and cult-like recruitment techniques.
Here’s one place to start some research https://en.m.wikipedia.org/wiki/Combating_Cult_Mind_Control