'Prepare for war, hope for peace' Plod are seriously being videoed by all sides these days, so they do have to be a bit less gung-ho. What happens is that those 10% 'kick off' because they feel that there is an army behind them - the police do their 'thang' and more people just get pulled in. I've been in a riot once or twice, from demonstrations, and you don't always have a choice about being in the middle of it. (I remember once demo where the people around me started chanting 'PC Blakelock, chop, chop, chop', which mortified me, and if the police had moved in, I would have been in the middle of a lot of very unpopular people)