Actually, by your logic, people on facebook would have to actively participate in a farming simulator, or have watched people farming over and over again and enjoyed it, in order for them to feel a compulsion (or if they were opposed to it, desensitization) to become a farmer, because it was fun to watch it happen and/or to do it virtually.
I have to say I have to believe there could be some truth to the statement that video games cause people to kill, except I don't think they cause people to kill, people do it all the time anyways, but after watching people be killed virtually, not matter how unrealistic it is, (to an extent, watching 2D guys being killed is a little different) it causes a change in young people especially. Now i've played plenty of killing games, and i;m not out murdering people, but by the time I did start playing them, I was already rooted firmly in the belief that murder is wrong, besides the fact I didn't play them obsessively (I played with a friend) like other people do, and it didn't effect me very much.
But when people let their young children, or children, play those games, without a guiding hand to at least tell them it's wrong, in neutral people it will just desensitize them to watching people die, which is bad enough, but in certain people, it could push them just that far and activate something. I know it sounds far-fetched, cause video game death and real death are pretty different, but, think about it.