Have a very good friend who was S&S deer using his long bow. He jumped a doe up and took a snap shot at it. He saw the arrow go flying harmlessly over its back. The deer tumbled over and died. It tripped and broke its neck. Happens.
Kieth Warren is kind of a dick. He IS a big defender of 2A. I like his twin brother Alan better. Nicer guy.
He was in an elevated stand. Shouldn't be a problem.
However, if he hits a rock behind his doe, a ricochet from a .50BMG is going to be a risk to someone miles away. A .223 or .243 is just going to come apart harmlessly.
A good bit of his hunting is done in Texas. I wouldn't be too worried about backstop. This guy knows how to shoot and hunt. He's NOT an idiot with a garage. Just because most wouldn't do this does not necessarily make it wrong or immoral.