It is also true that in a sufficiently lage population idiots will crack for no reason whatsoever. By attempting to minimize this guy's responsibility for his actions you give him support, just as those who claim that the homicide bombers in Israel are doing what they do because of some sort of action on the part of Israel give them support. Evil doers are responsible for the evil that they do. Being responsible for your actions is part of being a free individual.
First off, I am not minimizing his responsibility for his actions, I am merely explaining what happens when a random sampling of people are put through the meatgrinder.
But if you insist that your logic holds, I would then have to conclude that I'm supporting the actions of trolls every time I reply to you.