You missed the point. By a mile. What your animal does to YOU (or any other owner/keeper) isn't an issue. If you get killed by your snake and it is your own stupidity that does it "oh well". If however your animal is a danger to other people for whatever reason and you can't find it a suitable home it's time to put it down. If you can find an appropriate home, great! Don't put it down, there's no reason for it. But when your search has led you to the dregs of Craig's List I'd say your options have come pretty close to running out.
My experience comes from rehabilitating wild animals more than giant reptiles. I've had a run in with a few but never been concerned for my life with any snakes. I have however been on the wrong end of some teeth and claws one of which was a cougar that we had been rehabbing for almost 16 months from a cub.
Was it my fault I got attacked? Absolutely it was. Did I pay for it? Yeah I did. Did the animal pay for it? With it's life. And believe me it wasn't an easy choice to make but fact of the matter is that we had a supervisory board who recognized that the cat was aggressive and there was no way ANYONE could be expected to handle it and we couldn't take the chance that it wouldn't go right back into town among people.
I realize snakes and cats aren't the same thing. And I realize a cat is a lot more likely to be territorial, but you can't take the risk either way. That is irresponsible animal ownership. If I chose have a giant snake and it kills me, so what? But if it kills you then there is a problem.
Are you serious? You put down a cougar because it was aggressive?
Hell, with that logic we need to put down every carnivore on the planet.