This is a problem of separating fantasy and reality. If one understands that, say, Doom is a fantasy that does not work in the same way as the real world, then you won't have trouble realizing that you can't solve your problems with a well-timed shotgun blast while running at 90 miles per hour.
On the other hand, if you don't stop and think about how different Doom is from the world, then you get headlines about how Doom caused two teens to shoot up a school. Which, incidentally, is a bad example--the two teens you're probably thinking of were also neo-nazis, so it's far more likely that they played Doom obsessively because they wanted to kill people, and far less likely that Doom drove them to kill.
What this guy needs is a rude awakening. And, hopefully, he will get one.
From what I've seen, it's not the "murder simulation" that's the most significant. It's the spending of so much time within world-like environments where an amoral stance is consistently rewarded.
I've known people who have formed their moral framework almost exclusively from their experience within such environments. I've even known people in positions of power, who exercise power accordingly.
Games and VR environments are simply media. Media does have an effect on how we see the world, but it's almost never in the simplistic way that alarmists come up with. Rather, it's subtler, but it is certain to be there.