Yes, this is the ingredient that I believe many well-meaning educators are missing (as well as some of the unstable educators -- again, probably a minority of them, overall -- who may use the classroom to work out their own feelings of guilt and shame).

It's questionable how much the principal knew about the individual teacher's in-classroom approach before it became a public controversy. You're right that he obviously didn't want to rile up the parents; but, it's just as likely that there were some reasonable parents amongst the mob, he heard those voices out, and then he corrected the behavior/rhetoric (or, at least, attempted to) of the individual educator in short order. His public commentary may have been partially for P.R. purposes, as you suggest -- but it's also doubtful he wanted to see any problematic behavior reoccur amongst his faculty under his watch.