I have seen some examples of threads getting out of hand, and examples of passive aggressiveness on the boards. However, I find most threads to be fairly civil. (Mind you, I do agree with reporting offensive posts.)
One thing that I find beneficial is to consider that my views are based on my own experiences, and other people may have vastly different experiences. In the case of rules, some people may see an aspect of a game as a flaw and others as one of the games strengths. With this in mind, I try to base my arguments on facts, wand recognize that there are many possible interpretations. For example, some people love one set of rules, or a specific setting. Others do not. However, when I see a thread on one of those settings or other topics, I try to participate in a respectful manner. Regardless of our differences on the board, I think we all want to be treated with respect. In fact, I think most of the disagreements on the boards come about when someone perceives that another poster has been disrespectful -- whether or not that was the person's intention.
I try to recognize that people on the boards can be passionate. Sometimes, our passions can get in the way of our seeing the strengths and weaknesses in someone's arguments. I also believe in trying to give others the benefit of the doubt.
I think that the board benefits by having a diversity of opinions, and I have seen some great threads where people have differed strongly in their views or personal preferences yet treat each other respectfully. I think that we do have a lot to learn from each other. My general advice is to realize that not everyone will share your experiences or views, but that they deserve your respect as a fellow board member and a human being.
I think that most people on the boards want to have fun in their discussions and learn a lot from how other people have fun in their own games. While not everyone will like the same things, I think that this board benefits greatly from its diversity of tastes and opinions. So, I would suggest that we have to remember that sometimes our truths are a matter of perspective rather than absolute facts. In which case, I think that the best attitude to have is "I may disagree with you, but I respect you. I hope that you are having as much fun in your games as I am having in mine."