[swombat]

1) They weren't egging him on, apparently, just letting him get on with it without interfering.

2) This is a very well known psychological effect called "diffusion of responsibility". It's the same effect that allows hundreds of people to walk by while someone is being beaten up in the street, when almost none of them would just ignore the event if they were alone or in a very small group with no one else around. It's neither surprising, nor "wrong" per se - it's just human nature.