Chuck- I believe we want these animals to know the food they are fed is already dead so the snake won't go for something alive( a person )
Hmmm, I don't think so. Snakes act upon instinct. A snake which eats dead prey would probably strike a live one with more gusto. Although there are exceptions to this, wherein the snake is scared by the movement of a live animal.
As for snakes being trained not to eat people, I doubt it. Ask some of the giant snake keepers. I doubt they've got Monty trained to not eat them. There is always the risk of a bad feeding bite.
Although, I do have to agree that the way it sounds was that this guy was ready to rip out the mouth from the snake. Tsk tsk!