I am pretty sure _quasimodo's point was, idiots or not, it's barbaric to celebrate someone else's slow and painful death. Regardless of whether said person is civilized or not.
That goes a bit far. I can certainly feel excitement and amazement at their folly and not be barbaric. I'm thinking folks are transferring their horror at the predicament these criminals got themselves into, to the spectators reaction which was a pretty natural one.