While the looters themselves ran a broad church, racially, there has been a significant, and racially determined, difference in the way vigilantism is perceived, so that Turkish shop keepers, defending their premises in Kingsland Road (including one who chased looters off with a doner knife) are broadly perceived as doing an honourable thing. The men defending a Sikh temple in Southall are, likewise, admirable: I'm not trying to distance myself with the third person, I admire them. I admire the three men in Birmingham who were killed by a car, defending their homes.
When it's a large group of Millwall supporters, in a pub all day, talking about doing the police's job for them, it creates the impression that they're spoiling for a fight, opportunistically – using the chaos to bust into a racial confrontation that they normally wouldn't be permitted, in a metaphorical echo of the looters they're determined to stop.
http://www.guardian.co.uk/commentisfree/2011/aug/10/uk-riots-vigilantism-big-society?intcmp=239