Lead by example. My club has 60 members, so it's a slow proceess. It'll never change for some of them, but some guys look at you funny when you come in and tell them you saw 2 small bucks, they can't figure out why you didn't shoot them. Soon they realize it's not that hard to actually let a deer walk pass, it's not the end of the world. Some catch on and realize the benefits, some never will. Not much you can do in an existing club.

"In heaven, even the fish have antlers"