I am also keen to include guidelines on behaviour in the forums, such as respecting others views; being polite
I agree. In my experience, you sometimes have to teach folks how to disagree or question-- either explicitly through activities or implicitly through example, it depends on your audience. I teach teachers -- professionals with experience in the classroom, but not necessarily online. Even with their experience, it is interesting to me to note those who haven't any idea how to express a disagreement of another view or how to question someone's assumptions, and still respect the person stating the idea.