hahaha...you're kidding right? They are nasty snakes
The Cottonmouth snake is related to the copperhead but more dangerous. Venom is highly toxic with severe tissue destruction. Bites are fairly frequent in the southern United States.
They could have walked by it. Are you suggesting that every nasty animal that exists should be exterminated? The fact remains that the guy killed an animal for no reason other than to impress his kid.