There is a certain anonymity that is derived from being in a crowd.
Think needle in a haystack.
When people think they are anonymous, their levels of perceived accountability drop and behaviour can radically change. An element of peer pressure in crowds also eggs people on to do things that are outside their comfort zone and normal behaviour patterns.
Pretty soon you find people in mob situations doing things they would never dream of doing if acting alone. They become emboldened in mob situations and cross lines they would not even consider crossing under normal circumstances.
The problem is that once certain lines have been crossed they are very difficult to re-draw. Once civil disobedience is learned it's almost impossible to unlearn and all the more easily resorted to in the future.
