As far as I know, science has hitherto not conducted such an experiment and so has not disproven the supernatural claim that if a princess kisses a frog, it will turn into a prince.
Besides that, does the supernatural claim state that the frog-prince conversion will happen every time or just sometimes, say only once every 4 billion attempts? If something like the latter, the claim may actually be impossible to disprove. Or what if the princess and the frog must meet certain very narrow requirements? What if it’s possible only when the stars are suitably aligned or only at only a certain moment on a certain day of the year?
Then one must consider the scientifically established truth that humans evolved from frogs in the first place. An evolutionist shouldn’t have any problem accepting that a frog can turn into a human.
Here’s another way of looking at it: Those “Christians” who died after being bitten by the snake weren’t real Christians, but imposters. It’s only real Christians who are immune.
So line up 10,000 “Christians” and apply the ISBT (Infallible Snake Bite Test) to them. This will reveal who is the real McCoy and who is the fake. It will also demonstrate the truth of Jesus’ words, “Many are called, but few are chosen.”
I think it was St. Paul who was bitten by a viper while collecting firewood. When the locals saw that the bite didn’t affect him, they began to worship him as a god.