Yes, lots of people use them. Like any training device they are only as harmful as the hands that wield them.
I'll put it to you this way - some people think s GL is more humane. My dog can't stand it. She rubs her face on the ground, and gave herself an eye infection. They can hurt their necks and tear ducts and it can rub on their nose.
My pup never batted an eye when I put the prong on her. When I put the GL on her the first time she lay in the fetal position and refuse d to move. So which sounds more pleasant to the dog?
The GL bothers her all the time, whereas the prong only gets her attention if she pulls.
LOL about the vet.
Yes, dogs will frequently strangle themselves with their collars. You have to wonder...