We don't consider a clients' tag punched either if he makes a poor shot. It is the clients' call. We are real clear with our clients about legal issues, but don't try impose our ethics on them.
Haven't really had too many guys try shoot beyond their range in the past 30 some years either. Nearly all the hunters I've guided had what I thought to be a very limited range and knew it. One example of the flip side; got an elk up across a small draw, maybe 200 yards. I'm telling the hunter to find a spot to sit where he can still see above the brush. He finally glares and says "shut up!". He then puts 3 shots behind the shoulder of that elk with a .338 Win... offhand. When I asked where he learned to shoot like that he told me he had been an instructor in the marines and still shot regularly. Some folks actually can shoot.