Don't put all in that pool. I've been playing rated M games since I was 6 and I'm one of the most non violent person irl. Sure, there's bad apples, but that's same with any community.
I wouldn't say I'm the most non-violent person around, but I'm one of the least violent in actions. Doesn't stop me from wanting to kick people in the face, but I don't go through with it. I've played video games all my life, violent and non-violent. I've never been in a non-staged fight. Karate training matches yes, fights no.
Because I'm in Australia, the ESRB doesn't affect me. Over here, we'll get an MA 15+ rating (The highest we have for now) purely because it has guns in it. If they were laser guns, it might slip through with an M (one rating lower). But bullets turn practically anything into an MA 15+.
I hope there is some use of mature language. Doesn't need to be anything worse than, say,
Back To The Future, or nothing more than a word here and there. But having a group of revolutionaries running round screaming http://tvtropes.org/pmwiki/pmwiki.php/Main/GoshDangItToHeck would definitely ruin immersion. A few witty one liners and taunts can cover this up though, and completely remove any need for offensive language.
Blood isn't necessary, gibs won't be needed, swearing can be avoided. We'll still have teabagging 9 year olds whether this is rated M or T or E. So yes, I hope they don't add anything offensive purely to raise the rating. It isn't needed.