When it gets bad enough to have to fight back, something unusual (and undesireable) is definitely going on.
There is at least one "religion" that undoubtedly deserves all the derision and contempt it gets but, even in that case, it is not a teacher's right nor his expected role to use his position in class to do so.
As for teaching morality in class, that is a minefield. I wouldn't trust anyone from the pervert persuasion to unravel ethics or morals --or religion-- for my children.
Back in the dark ages, my 9th grade biology teacher had to teach reproduction. He was very clear before he ever started. Said I can tell you the anatomy and the physiology, what parts are and how they work. You need to talk to your parents about everything else. He drew the line very clearly and diverted questions (even from the “tough kids”) that moved into morality.
I still respect him for that. After all it was a public school in the 70’s.