It's not so much the beliefs that people hold, it's whether or not they stick to those beliefs in the face of mounting evidence to the contrary. If they do,

It's not so much the beliefs that people hold, it's whether or not they stick to those beliefs in the face of mounting evidence to the contrary. If they do, then their reasoning is not based in reality, which makes any other reasoning they do that is also purportedly based in reality suspect. Most human reasoning is not based in reality. It is very difficult for a well-educated and intelligent person to even approximate rational thought; see sites like < http://lesswrong.com/ http://lesswrong.com/ > to see how much effort is required. All claims to reality-based reasoning should be regarded as suspect, unless accompanied by sufficient evidence.