As a kid, I remember it being spun as "don't mess with evil."
But as an adult, it seems like a rare (and perhaps valuable?) counterpoint to "don't judge other people" or "don't judge a book by its cover." Sometimes... those behaviors are adaptive.
It is weird because the scorpion, of course, dies too. And the frog was just doing him a favor.
I think the moral is supposed to be: "Some people are just irredeemably awful to the point that they'll self destruct and take you down with them if you try to help them" which... I guess is true but pretty jaded for a children's story, haha. Although, old fashioned fables do tend to have that dark aspect.
But as an adult, it seems like a rare (and perhaps valuable?) counterpoint to "don't judge other people" or "don't judge a book by its cover." Sometimes... those behaviors are adaptive.