The one time I've ever held a snake behind the head other than applying meds was when I had to very quickly move a large wild rat snake; he was in a bad place, and I was wrangling him while simultaneously fighting off a pack of chihuahuas. Yes. A pack of chihuahuas. Plus there were people around who weren't very fond of snakes, and getting tagged in front of them just cements the idea that all snakes are dangerous.

They are very difficult to hold onto that way, and it isn't safe for you or the snake. If you try it with a wild one you run a pretty high risk of getting tagged or injuring the snake.