I work on the basis that the pilots are extremely well trained to fly the plane and the cabin crew equally well to run it safely and to provide a professional service to passengers.
If a member of the CC is having trouble with an errant passenger (which in 30 years of flying I have never seen), I would try to help if requested.
Otherwise, I would keep my nose out of it on the basis I could be viewed as a sanctimonious prig.