For one, Slashdot has a bunch of anti-social jerks that like to post, who have an inability to empathize with anyone else. So no surprise they think something like that is a good idea, because they they aren't very reasonable people.
However others have pointed out, accurately I think, that something like this can well be a cause for it. The thing is that if you push someone in to a corner and give them what seems to be no way out, no way to fight back, they may go nuts. Happens with other animals, not just humans. So if you have a kid that is continually picked on, who tries to stand up for themselves, but is then picked on even worse, this time by law enforcement, well then they may well take drastic measures because they feel like there's no option, no hope.
I think there is some real merit to this. Not merit as in saying it is good that kids do it, but that it is correct that actions like this can lead to kids doing it. If they feel they have nothing to lose and nowhere to turn, then a completely crazy overreaction may be the only option they feel they have.
I mean here you have a case of a kid who did everything right, and got increasingly screwed: He never fought back or defended himself, which schools do not allow (you can argue if they should, but they don't, it is against the rules). He got no help or support from the school, I mean it was allowed to happen IN CLASS in front of a teacher. He told his parents, they were skeptical, he produced evidence. He was then threatened by the police, ordered to delete it (illegally), drug to court, etc, etc. So what has he got now? He's been effectively told the bullies are allowed to do as they wish and if you attempt to stop them the police and courts will punish you.
So what's he to do? You can see how a drastic, illogical, action might be what he thinks is his only option. Remember that he doesn't have the perspective of age, he can't look on high school and say "Ya that's a real short time in your life and it gets WAY better once you are out and an adult." To him, this is his whole world. And for that matter, the adult world has stepped in and told him he;s wrong to try and make things better for himself.
As such you can see why people are saying it can lead to something like a school shooting. It is something that administrators need to consider: Dealing with bullying isn't something to do just because it is the right thing (which would be a good enough reason) but it is a safety issue as well.