If I'm a brilliant mathematician or a world-class athlete and I choose Kansas over Cambridge/Boston, then yeah, plenty of people are going to think that my attachment to Kansas is making me act irrationally. I don't think they lack a "modicum of intelligence" because of that thought.
There are obviously exceptions where your choice of location doesn't matter, but if you're a high performer then it frequently does (with the obvious notable exceptions e.g. Prince).
[EDIT: I originally just had a quip about not being a sports fan, but I thought you deserved a real reply.]
In particular, if you're an academic mathematician and you ended up in Kansas, then that probably means that you're working at the University of Kansas or Kansas State University.
Nobody with a modicum of intelligence thinks that is irrational. Of course people are going to have strong attachments to a place where they spent a major portion of their childhood making memories and relationships.
The only seemingly irrational thing would be indifference. You don't spend 18 years in a place and not have any emotional reaction to it (good or bad).