Perhaps show him the bites from an adult anaconda or a similarly sized snake, such as a retic (here's a nice example-- 25 stitches and $17,641 in medical bills from a 17-footer)? It's silly for him to think he'd be immune from the anaconda's bites. If he's inexperienced to begin with, that probably jacks up the likelihood far more, even if the possibility is always present no matter how calm the snake. Maybe tell him that to even consider it he should build up from the basics-- even the smallest of which have teeth, and if he can't handle that, there's no room for a snake in his life!