To be fair, crappy parents are the real problem. However you can't blame it on the parents and let it rest at that, because that won't solve anything. If one kid shoots another kid because they played some game they shouldn't have, it isn't the dead kid's parents fault in any sense, and often they have nobody to blame.
Still it is the case with crazy people that they will latch on to any violent stimulus. It's not like there isn't really extreme examples of violence in literature or in movies.
I guess the problem is that games are (a) interactive, and (b) a new medium, so that's where the controversy comes from. Personally, there is another very interactive medium that a lot of these legislitive people discount: Human imagination. There is not a violent (or sexual) thought that a (sick enough) human couldn't reach on their own without any prompting from outside ideas, so all in all the violence-in-games thing is a little bit moot.
Although I think Jack Thompson is totally fucking insane and a lot of his points are extreme and put across in a logically incorrect or controversial way, I do think he has some good points about restricting the sale of inappropriate material to minors, and on profiteering on violence.