Observation on smart people, with an example from smart fandom

Why is it that the same people who are willing to accept their own areas as difficult, structured disciplines are so often unwilling to extend that point of view to the disciplines of others?

• Physicists arguing sociology with people who've actually done studies on millions.
• Archaeologists arguing statistics with mathematics chairs in same.
• Brilliant computer geeks who happily argue with lawyers using arguments that, if they were actually how law worked, would end society in fire.

I realized there's a nice fiction parallel with which we're probably all familiar; I recast this question in its terms, below. The foregoing and the below are subtly different questions, so have at it either way. My comments in the comments. ( Respect for fictional vs. real disciplines )