Even if a doctor's belief in the stork theory of reproduction is technically irrelevant to his competence as an eye surgeon, it tells you something about him. It is revealing. It is relevant in a general way to whether we would wish him to treat us or teach us. A patient could reasonably shrink from entrusting her eyes to a doctor whose beliefs (admittedly in the apparently unrelated field of obstetrics) are so catac…
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 . A Creationist can not perform what he thinks is correct science without performing what the rest of the world is incorrect sc…
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/ > to see how much effort is required. All claims to reality-based reasoning should be regarded as suspect, unless accompanied by sufficient evidence.