Insisting on a please and thank you atmosphere reminiscent of a sunday school outing is not necessarily the answer either.
That might be too much to bear, but I think I could suffer through it for a week or two, actually.
Another thing is the notion that we all have to agree on things. I don't want to start hauling out examples, but I don't think the end result of every discussion needs to be bringing everyone around to one point of view. Sure there are core values which most of us share, but there are far more things on which we do not all agree. The point should be to understand and learn from each others' position, not necessarily convincing others that yours is the absolute truth.
And for that matter, I have often learned some of the most important things about issues form people whom I completely disagree with.