Based on my understanding of tenure and the fact that the guy already had 19 years of work under his belt (thus suggesting he has tenure), and the fact that Kansas has a tenure system, I'm highly suspect of the whole argument he gave.
You gotta do some pretty bad stuff to get fired after getting tenure. Bad mouthing the president will not get you fired if you have tenure. One of the biggest digs against tenure is that it allows teachers to get away with a significant amount of stuff. Unlike private schools who can terminate for pretty much anything, tenure protected teachers have virtual ironclad protection.
I suspect this guy did some stuff that the school nor him want anyone to know about. Like having inappropriate relationship with an 18 year old female student. Or embezzling. Or lying about his credentials. Those will get you fired even if you have tenure. Voicing your political views will not.