> people who push (even gently) to get closer to some stage/etc actively and lethally endanger others for the sole purpose of being closer to an amusement.
Completely false. The reason people don't die at a concert is because the organisers control the crowd density. The density is high, but not so high that death is all but inevitable (as was the density in Itaewon on saturday, which can be confirmed from photographic evidence of the scene).
They have crowd barriers and security staff and it's well lit, so they can see if anyone is struggling and help them over. Even if the crowd density is relatively safe, localised disturbance (eg. someone tripping over, losing a shoe) etc can cause a dangerous situation. So even when the density is at a level considered "risky but safe", you need vigilant security staff and a space to overflow people to (space created by crowd barriers.)
If the density is too high, or the measures to protect people are insufficient. It is the fault of the organisers, and that is manslaughter.
This is just called "risk management", you tolerate some level of risk, so that people can do the activities that they enjoy, while allowing them to have the reasonable expectation that they won't die.