Half of teachers being outright hostile to students is far too many, in my opinion.
How does this behavior positively impact the lives of their students? Do they not understand the psychological damage they can be inflicting? Do they simply not care?
Adolescence is an exercise in accumulating scar tissue. What you call damage, I can argue is growing up. You need a thicker hide and a more independent source of self worth; reliable continual external validation inhibits, imo.
Teachers are just other people too. The sooner teenagers recognise it fully, the better placed they'll be to choose their own way rather than have it chosen for them.
If it's done in a respectful, consensual manner then sure... there's nothing wrong with friendly harmless teasing. The problem is that it often crosses a line into bulling with zero net benefit for the victims.
Saying something like "What you call damage, I can argue is growing up" is a dangerous phrase; the type of dismissiveness that gives me the impression that you may have difficulty with respecting the boundaries of others. Could you please provide a couple of examples of the type of conversations/comments you've made that helped people build a thicker hide? Have you ever been thanked for it?
That said, adolescence is absolutely not an exercise in accumulating scar tissue so much as learning through trial and error how to interact with others, gain an education, and learn life skills to become a functioning member of society.
How does this behavior positively impact the lives of their students? Do they not understand the psychological damage they can be inflicting? Do they simply not care?