I enjoy a good discussion on religon or politics. Sometimes both at the same time...
I've found that we generally run into problems when we encounter one of two types of people:
1. People who aren't interested in facts, opinions or anything other than their own position. They can't offer anything other than a party line, whatever thatline may be. I generally don't engage these type people as I really don't find that they have anything to add to the discussion. It's unfortunate, because they've clearly got a passion for the subject.
2. People who get so wrapped around the axle when confronted with something that they don't agree with that they instantly resort to name calling and personal attacks. We've had a lot of this around here lately, and it's frustrating.
My admonition to both of these types of people in PMs before taking an administrative action is usually to either get a better position or better rhetoric. We welcome healthy debate. I just want to see people add to the overall conversation.