The job of high school principal is one, also, where I think there should be space for someone's private opinions to qualify or disqualify them for the job, just because of the enormous trust and power we place in them. I'm not sure what I think about these comments, but in general I think it's fine for us to be more cautious with schoolteachers. Especially because he currently has a job with the same school district on "administrative duties", I expect that if he expressed the same opinions as a back-office employee with the district, or in many other individual-contributor careers that do not involve management or oversight, he would have been fine.
I'm curious how we can measure that it's getting worse. In 2003, this teacher was fired after sending an e-mail (we had no Facebook back then) with certain distasteful remarks about race, and claimed to be a "victim of political correctness":
https://news.google.com/newspapers?nid=1696&dat=20030308&id=...
In 1995, this teacher was fired for making a single, though completely unacceptable, comment to some students with racial slurs:
https://news.google.com/newspapers?nid=2519&dat=19950130&id=...