I must admit this is not just a trout fishery issue as i do various types of fishing and often see mis/bad handsling and not just from newbies to the sport.
I have seen seasoned anglers still handling fish with dry cloths or in trout case just being hauled up the bank then released.
This is not only bad behaviour but bad for the sports name in general,it does not take long to hold a fish and unhook it without any ill effect on return.
If wading then this job is even easier with minimal fuss.
There is no excuse for this treatmwent even if your intentions are to take the fish home,i do prefer catch and release and i no there are arguments for and against this either way the care of your catch is important.
If you see any bad angling then please mention the correct way to this person and make it clear that you are not a busy body but only trying to help.
people i have seen pulling trout up the bank and then releasing them when clearly have a net at there side want banning its not just lazy but downright disgusting,people who clearly have been an angler for a long time should also note that a towel/cloth is for hand wiping and not removing the fishes protective barrier of slime.