I haven't watched the video, since I'm at work, but that does indeed sound quite horrible. The explanation as to why it happened is even worse.
It's things like this that make me wonder just how far humanity will make it before it's strangled by the psychological holdovers from our ancient past. In order to survive as cavemen we had to be selfish. We had to hoard our resources and only render help to those in our "group". To do otherwise would endanger your future.
There is enough "wealth" in the world that this need never be the case now, but because of the way humans are programmed we can't do that. We could never spread all of the world's wealth evenly among everyone. It just couldn't happen, because people are people. There are just too many people who will do whatever they think they can get away with to put themselves at an advantage to everyone else.
The bit about even needing good Samaritan laws is another prime example here. There shouldn't have to be a law protecting you from trying to help someone. But people are people. I understand that China is different from the US, and there are a million nuances to the Chinese situation that I'll never know or understand, but that transcends culture and place.
The unfortunate part is that by it being part of our nature, I don't know if we'll ever be able to overcome it entirely. The only real solutions would either have just as many drawbacks or would never be accepted (such as forced worldwide directed evolution, how would you even accomplish that?)
Wow, that was a tangent, so at the expense of having wasted a small essay, I'll say that I don't know what I would have done in that situation. In all honesty, I'd have probably done the same thing as the onlookers (if close to a score people did something, there's surely a reason behind it). I would like to think that I would at least notify emergency personnel, but I have no idea how that works in China and for all I know one of the onlookers actually did this. There's not a lot else you really can do and make a difference.