I don't think it's ridiculous to be concerned that children are spending their formative years brutally murdering semi-realistic-looking people all day. Generally the sort of activists inspired by this concern are horrible people though.
The vast majority of gamers in 2014 are adults. I read a statistic a bunch of years back that there are more females over 18 that play video games regularly than males under 18. At this point I'd even be willing to wager there are more gamers over 30 than under 18.