Great to have a thread like this one because we do come from a variety of backgrounds, and therefore, not everyone knows how to conduct themselves on the 'net in a way that tends to come across as respectful to others.
I'm going to add a little by bringing in specific guidelines used in online (graduate level) courses I've taken. The idea is to explain specifically how to express oneself professionally, with consideration to that fact that students aren't expected to know these things in advance because they come from different backgrounds.
1) The difference between debate (which is productive) and bickering (which is counter-productive) basically rests on whether you criticize the statement being made or the person making it. Try to avoid singling anyone out or saying anything that could be interpreted as a personal criticism. Instead, it's best to reply to a statement you disagree with with something along the lines of, "I disagree with this. My personal experiences and / or what I have read indicate otherwise," and elaborate with facts gleaned from your own life, not assumptions about their life.
2) In keeping with the above, I think it's often best to avoid use of the second person and generalizations in any context where it would be equally effective to simply speak for yourself. For example, "In a similar situation, I did ____ because this is my take on the subject . . . " instead of, "You should ____ !" or "People in that kind of situation are ____ , so they should ____ ."
3) Whenever you have the time or energy to find articles or similar resources to back up what you're saying in a debate, do so. This helps others to educate themselves and it shows that you are simply making a statement based on information that you find useful, not attacking or criticizing anyone.
Not from my online classes but just from my experience with forums in general:
- If one finds a particular member's posts to be bothersome in any way, it is possible to simply make a habit of choosing not to read them. I've noticed that sometimes, people forget this and may, as a result, make enemies when this could have been avoided.
- It is possible to be supportive and disagree with someone at the same time. One can always say, "I, personally, wouldn't ____ because of _____ , but I recognize that it's a challenging situation and I wish you the best of luck with it."
I think polite debate is a good thing because it often causes people to think about things they wouldn't have otherwise, and hence make better-informed decisions. But I think it's important to think of a response to a debate-type topic as "offering a different perspective", as opposed to "promoting your own beliefs".