Hey. No .. you should take up this issue...

Kids persanality completly depends on the adult behaviours he/she is experiencing. moreover this can damage his slef respect and kill his confidence.

I would suggest to talk to the said teacher personally. and request in a very polite and diplomatic manner. You can convey that the kid is all scared and keeps crying and is sleepless due to his behaviour. Instead of sounding a blame , put it on the kid saying he has not gone through such situations in his life which may be the reason.

If this still persist, join with the other parents who has the same concern and address it to the principal and strongly suggest to to change the teacher.