I'm not infallible.
On the rare occasions I am wrong on a subject I own up to it. Normally though if I am arguing a point it's because I know I am right.

I make certain of my side before I go head first into an argument based on hard data or science. That is why I normally can come right back with information supporting my side. I don't go off arguing points of fact I can't prove with hard data or scientific proof because that just is not logical. I also don't argue using biased marketing theory and strategy.
Now arguing theory is different because it is just that. A theory or scientific hypothesis. If you don't bring up ideas like that for round table discussion then nothing gets settled or hashed out. Then many parties can discuss & back their theory against each other and many times all the parties involved have many of their points by correct even if the overall theories are opposing.
If one was not confident in their own thinking then they could not do their ideas justice. Just because one is confident in their intelligence and thinking does not make them "holier-than-thou"