Would you rather take a chance at greatness, or a certainty at mediocrity?
No guts no glory.
No guts no glory.
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.
Everyone parents differently. I would be interested to see which culture the "laughing" reaction parents come from.