You must not see the humor in a lot of monty python skits...
When your cat races around the room and runs into a sliding glass door, then gets up dazed and still trying to act cool, like it MEANT to do that, you dont get a giggle?
The fellow in question did something stupid... much slapstick ensued and in the end he was, yes, in some pain.... but not permanently injured- laughter is often a natural reaction to unexpected situations- that had to have been a VERY unexpected for all of us watching it...
He tried to act cool about it afterwards- claiming that the pain was no worse than eating a hot pizza- all the while pausing to apply a tissue to his bleeding tounge.
The laughter only came AFTER it was clear that he was 'ok'... during the incident all we could do was watched stunned.