I have never read the rules, working on the principle if you are a valuable member of a forum things will be OK, if you are too vitriolic or aggressive then you will get flamed, however..........
In the spirit of open debate I do not think it is healthy to moderate too heavily, for example if one person has an opinion out of kilter with everyone else's. That is the real benefit of a forum like this, we get pushed, challenged, have our eyes opened to new ideas and are subject to new blood and new influences.
In the past I have been shot down, had fairly vitriolic arguments about V8s and several other things but we are all big boys (and girls) here, we should be able to stand the argument and more importantly learn stuff along the way. Besides, it is healthy to argue, debate and articulate your own point of view.
In actual fact, the people I had the most vitriolic arguments with are now people I exchange emails with offline from the forum, we learned how to cope with each other's views and found that we quite liked each other and actually had much more respect for the other person's views than ever we thought we did to start with.