Like ehbeth said, it is sometimes hard to determine whether a poster is actually being emotional. Without the use of facial expressions and inflection, we must rely solely on the written word to determine the context of a post.
Sometimes, we become frustrated because someone we are attempting to have a discussion with doesn't seem to understand what we mean. We, in turn, don't really understand what they mean and another poster may come in and not understand either and post something that they take afront to.
Soon, the otherwise peaceful and academic forum room turns into the OK Corral or the old west saloon. The gloves come off and anybody in the way gets it.
Many, I suspect, are misread and are viewed in a particular way that they would never be viewed if people spoke to them in real life. That is another thing. The anonymity of a forum with made up monikers opens people to act in ways they may not do in real life. Something like drivers who become all powerful in the safety of the vehicle of which they find themselve behind the wheel of.
Some may be like drive-by shooters who make a single comment that causes emotion in someone. There are some threads that are, apparently, started with the intention to incite and the author doesn't really care about the opinions of those who reply. There is one poster in particular who does this. The threads generally progress from simple dialogue to heated and nasty comments and innuendos. I hven't seen many who are beyond this.
A2K is going through a transistion of sorts right now and the "emotion" seems, at least to me, to be at an all time high. This too will die down.