"I wonder if future reporting will include an accounting of how many disappointingly predictable liberal teachers attacked military children. Two? Ten? Twenty? Forty? Out of how many hundreds? One is too many, but still, blanket condemnation of teachers because of the behavior of some is just as destructive as the attack on children is hateful."

The difference is that the teachers are suppose to be adults.
There is a difference in speaking in a meeting and speaking as a teacher in a classroom.
A teacher instructing the class on their political or religious view is bad teaching- the lower in the grade the worse it is.
It's not merely the children might be aware that their teacher "might" be hostile to your parents- because say the teacher spoke about some issue in some forum other than the classroom. It's not merely that the subject is a "mature topic".
The kids are in a classroom. They are graded on getting the right answer. The right answer is the answer the teacher thinks is correct. A class has other children which have relationships with a kid (peer pressure). The parents are sending their children to school. School time is a large amount of time in their life. Learning is important and will affect their entire life.
Besides all the above. The miltary deserve respect. These guys & gals are putting their life on the line to support our national interest. And we don't need our public institutions attacking the people serving in uniform- that's the "job" of our enemies.