I think one thing that we run into as far as both drugs and Anarchy are concerned is that people on both sides tend to completely ignore what the people on the other side have to say, at least as far as the person on the other side can tell.
Sometimes this is because the person on the other side is saying something that has already been said, and thoroughly rebuked, in which case linking to the old thread where that happened is a far better response than the usual response (basically, fuck you you brainwashed moron) Other times things get ignored because the people on opposing sides have taken a personal dislike to one another and can't really pay attention to anything the other says because it is colored by "this person is a brainwashed moron and has nothing useful to say" That last is, IMO, where most of the real screeching comes in because people end up reiterating points that have legitimately not been answered at one another while ignoring one another's points because there is no longer any respect for the people on the other side of the issue.
being nice isn't required for communication, nor is it required that people like one another, but a certain amount of respect is vital or the whole conversation just becomes a shouting match.