Posting on a forum entails using etiquette; it's easy, without the nonverbal component of communication, to mistake a poster's tone or intention. It is important to exercise respect when posting, especially if the discussion is becoming a heated one. Personal attacks, sarcastic one-liners, general rudeness, deprecating statements, and the like are useless in terms of information and facilitating a constructive discussion, and can constitute flaming in particularly heated discussions.
When posting it's critical to remember to stay focused on the topic of the thread, and not get off on tangents, or start attacking someone personally because they have a different opinion. In fact, differences in opinion, when handled in a mature, non-inflammatory fashion, can lead to a highly informative thread and a more cohesive, comprehensive and therefore accurate picture of the topic being discussed, as it's being addressed from several different angles and (hopefully) scientific sources or expert opinion/knowledge is being introduced.
Respect ensures an informative, useful thread, while rudeness and flaming accomplish nothing and actually generate more work for staff, as they often end up having to step in and put things back on track when a thread degenerates into an inflammatory back-and-forth between/among members, and in extreme cases provocation of moderators and staff in general.