Some people are more impressionable than others, and as a species humans are pretty darn impressionable. Just look at history, and well, organised religion is a good example (not trying to start wank, but you have to admit people can get really impressionable when it comes to religion, especially when they organise). That's why cartoons and tabletop rpgs get blamed for so much junk - the truth is, SOME kids really are affected and while some are not, that doesn't change the fact that some are. It has been shown that after playing a violent video game some children gets all worked up and start running around hitting eachother, breaking things etc, although this typically only happens - as with war and the abovementioned organised religion - when those children are in GROUPS. A person sitting alone playing a violent game is more likely to walk away calmly than someone sitting there playing the same game surrounded by other people either playing the game and getting worked up or just watching it and getting worked up. Excitement feeds excitement. Of course there have been instances of a lone person watching violent movies etc and then going out and shooting people from a tower, but those people are generally proven to have had issues beforehand.
Humans are fascinating.
