There was one time a lady wouldn't tie her lease horse.. she'd wrap the rope like a coil around the post and walk off to do whatever. Well her horse got seriously tangled and pulled himself tight and got his foot there and his head was here.. it was a mess. So I went over, untangled him.. and then told the lady she shouldn't do that because I just saved him from a nasty pulled muscle, or worse.
She didn't from then on, she was actually thankful.
Another time, a horse spooked whilst tied and her owner was grabbing brushes.. this gelding went tearing across an active parking lot and found some grass but was too nervous to eat it. I took Sky's rope and caught him, brought him back and the owner saw me holding this horse by the jugular with a rope. I was honest and told her what happened, and she was SO happy because her horse could have gotten hit by a car or broken his leg in a pot hole or worse!
I've also had people yell at me and never talk to me again, but that's because I am young, they were older and they were embarrassed.
But like I said, rather get slapped in the face than have someone really hurt.