I think part of the issue is not just the "reactor" (i.e. the person who is doing the reacting) but also the originator. Example: A person loves Steve Roach's music. Someone else on a forum writes " I don't like Roach's music. I think it's boring." As the reactor, a person now has the opportunity to engage the opinionated poster with one of two approaches "Why do you think it's boring?" OR "Well, you just don't 'get' his music, obviously."
This kind of thing is always a two-way street. No matter how incendiary an initial comment can be, e.g. instead of the example above, suppose the first comment was "Roach really sucks. He's a no-talent ass clown." it's still up to you, the "listener" to decide how to react. Yes, the second comment appears to be mean-spirited and, at least in your opinion, it may also be ignorant and abusive. But, IMO, you only show your insecurity if you counterattack, so to speak (and this 'wisdom' is coming from someone who used to counterattack all the time, so I am pointing the finger at myself too). You may feel threatened by a contrary opinion or feel at least somewhat compelled to "defend" your opposite view. The latter is fine as long as you don't 'come after' the person. After all, it's just that person's opinion, really.
If I were to write "Sarah Palin is wholly unfit to be president." you might disagree with me and state that. But if I write "Sarah Palin is an idiot, but she sure is one hot MILF who I would happily nail." you might, if you respect her, want to come after me. It's totally understandable because, as humans, we have feelings and they get aroused. But, remember that your reaction says as much about you as the initial comment says about the poster.
At work, since Kathryn works in the same place I do, I hear negative things about her and about her department. As much as I want to defend her with passion, I need to step back and only make my own contrary opinions known in a calm, intelligent manner.
OTOH, in some forums, e.g. fark.com, flame wars erupt and they are almost done in the spirit of a "game." Obviously, the Hypnos forum is not like that and I respect that. Not all people find that kind of thing entertaining. But, it is sad that incendiary opinions can spiral downward so easily, as they seem to here. Frankly, I don't care what people say/write, no matter how "out there." I would only feel the need to disagree vehemently if I felt someone I knew personally (emphasis on the personally part...as I don't feel I know hardly anyone here that well, except maybe Jeff Pearce) was being attacked via patently untrue statements. If someone wants to opine that a musician is either (a) highly talented or (b) talentless and I hold an opposite opinion, I would just say that and be done with it. Same thing with an elected official, etc.
Lastly, it would be great to see people just be able to joke around with each other, even when virtual "tempers" flare. Life is too short to get that angry about someone just because you don't see eye with them.