Do children understand that nuance? I would have thought they would associate people falling with laughing
Obviously you don't laugh with big falls and broken arms.
But from my own childhood I can remember that kids are not subtle - if they are mocking you, you will know (names, finger-pointing, jokes, etc.). Whereas if a friend laughs with you about a silly fall, you get a completely different kind of scenario played out.
Coming back to your initial point, and being blunt: showing your children that clumsy falls can be funny, and not to panic about them, does not increase their cruelty towards other kids.