Even if this sounds ignorant: I don’t care what scientists say to this, there is no link.
How dumb do these people think gamers are? If a fictional work of art would influence people in such a simplistic and linear way, we would’ve gone extinct thousands of years ago after the first theatrical play depicting the war against another tribe or something, because everyone would’ve gone on a killing spree. Even little children aren’t that dumb.
The only thing that influences people in a certain way are the emotions or thoughts provoked trough the story or the presentation. It are ideas that lead people to certain actions, the mere explosion of a head does fucking nothing.
For example: I can have fun all day long with gutting stinking demons in Doom with the chainsaw or tearing their limbs of and beating them to death with it and not waste a single more thought on it when I go to bed. What really sticks in my mind are certain scenes (like the prologue or the ending) in The Last of Us. This is the kind of brutality and cruelty that leaves an impression in the players’ mind. It depicts far less blood and dismemberment than Doom, yet I would deem it to be far more brutal than the afore mentioned.
And let us not forget how twisted and disturbing the original grim tales were. So much for videogame violence being such a new and different thing. And let us also not forget that these tales were actually written for children, whereas shooters or horror-games were not (another thing anti-videogame advocates like to forget).
Btw.: this dude on the left was allegedly in the military and thinks you can train shooting with games?! I never touched a gun in my life and even I have enough common sense to know the huge difference between moving a mouse/clicking a button and pulling the trigger of an actual gun.
Edit: Rewatching this, I noticed that he didn’t actually say that, but he is clearly insinuating it in my opinion (at 1:33).