I cannot see any thing funny really and symphatise with the rider as its just one of those stupid things you do.
I once tried to push a road works sign over many years ago when I was young and full of beer as I rode past it on my bike, next thing I knew I was sprawled across the road with my bike on top of me. I did not know it had been weighted down with a load of sandbags and was immovable and stopped me dead in my tracks.
Only joking on my first sentence, other peoples misfortune is always funny.