If I remember correctly, the worst part of it wasn't just that the toddler was thrown, but all those people were either running to stop that woman from being stabbed, or were running to rape her and ran off because one of them got shot by a passserby or something.. (Canne remember where I saw/heard that)
It looked like he was trying to rob someone. And then out of the commotion people ran in but the guy ran out and (I'm guessing) that he threw the kid as a distraction.
It's not funny that the kid get's hurt, but it does look funny, unless you are some kind of overly sensitive dick.
This would be a typical thing in a movie, and people would find it hilarious, because it looks funny. It also looks funny here, it just so happens it isn't funny in real life.
I think it was funny because of the surprise element. All the time I looked at the toddler and thought : "He will probably kick him to make them waste time so he can run away" But it went soooooo much further then that.