I don't disagree that gamers could maybe have stood to be a bit more mature in the face of his criticism. In fact, the criticisms themselves weren't fundamentally unreasonable, just his behavior. As games continue to become more mainstream, we WILL need to look seriously at the possibility that games might have an effect on the people who play them. Perhaps not to the extreme that you will become a deranged gunman if you are exposed to Halo too early, but we do need to bear in mind that media has a powerful ability to impart values, often in very subtle ways.
Obviously this does not mean that a significant number of gamers at risk of becoming people who think that murder and violence are fun. No one thinks that. But people will take moral lessons from the media they consume, and if one such lesson is that aggression is the only way to deal with adversity and that problems typically break down to "good guy, bad guy", then I think it's not unreasonable to worry that that person may develop to be less agreeable and disinclined towards compromise. On the other hand, we also have games that emphasize things like teamwork, planning, and perseverance, and players may also take away those values. There is important discussion to be had about topics like violence and sexism in games, because while those things perhaps do have some importance, we need to be careful with what messages games give to players, intentionally or not.
Anyway, Jack Thompson. Well, maybe he didn't deserve the treatment the community of gamers gave to him, and the fact that gamers don't always respond well to criticism remains a problem to this day. I don't believe there is any justification for harassment and hostility. That said, I have little sympathy for him. Thompson did not make reasonable criticisms of games. He was not giving an academic and critical analysis of the media for content creators and players to think about.
Instead, he was at the scene of the Virginia Tech massacre, one of the deadliest acts of school violence in US history that left 3 dozen innocent people dead, to lie through his teeth that it was because the killer played video games, which was almost completely untrue. He showed up on major news programs to slander developers and players based on outright lies about video games, such as to claim that Manhunt 2 was a "murder simulator" that a bunch of children would play (it turned out that the game sucked anyway and that very few people actually played it), that GTA is about killing policemen and prostitutes, and that Mass Effect was a pornographic sex and rape simulation. He harassed and threatened several game developers. He was more interested in pushing his moral agenda through bans and censorship than improving the medium of gaming or looking out for the people who play them.
He has no one to blame but himself for losing his license to practice law.