As I've mentioned before, I was a sports official for years. President of an organization that represented 7 sports, and I can tell you from experience, Beisboll Umpires are THE most stubborn and egotistical of the lot. (Basketball would be next)
I think this is due to the fact that Beisboll is measured in increments under an inch... the strikezone is tiny, the calls are so tight... and Umpires are REALLY exposed... so they grow a shell, and develop an attitude. It doesn't help that the idea of "kill the Umpire" is so deeply embedded in our culture, and that's what Beisboll is more than anything else... EXTREMELY traditional... conservative even.