This might only be tangental to what you're talking about, but I think some people might have not immediately visualize the risk factors that contribute to the problem.
This is even close to the density of the trains around Shibuya during rush hour.
Famously, station attendants will push stragglers into the car in order to make the doors close.
In NYC, if you were to have more than one square inch of your body touching someone else, that would be the grounds of an altercation. During rush hour in Tokyo, the concept of physical personal space is universally diminished when everybody knows that you're going to be scrunched up as tight as possible to the people around you, so just live with it and not make a big fuss out of it.
In that image above, you can see how it's a physical environment where's the a huge potential for accidental or criminally deliberate inappropriate contact. Like you mentioned, it only gets more complicated when you add alcohol to the mix, or have victims that may be more likely to remain quiet of our embarrassment/fear than to yell in someone's face and bring the mob into it.