I consider reasoned debate an essential way to keep from fooling ourselves. It is also a way to hear many different sides of an issue without being "so open-minded that our brains fall out."
It is essential in a technical design process (especially in defining project scope). It is essential in policy making. It is essential in the court-room. I think it is essential in any context where we don't want to fool ourselves, collectively.
However, many bright people are intimidated by debate. I used to be much more so, when just I got out of college. I am trying to remember what I found so intimidating....
Sometimes by sheer-volume, of data or information, I was afraid to enter debate or some form of intellectual discourse.
Sometimes, the debates turn technical and I feel I have so little notion of what is being talked about that I cannot contribute (even if I have some intuition that people are fooling themselves).
Sometimes, I get the feeling that people are more interested in "winning" than exploring the merits of a particular viewpoint.
Sometimes, I think people take the debate as personal attacks on themselves. Sometimes, people do attack others personally.
What causes it, and how can it be avoided?
From the standpoint of a person who doesn't make the rules of order in a debate, how can we reduce our intellectual intimidation of others, and become more resistant to intellectual intimidation ourselves?