Im getting rather lazy at typing out my arguments and this guy sums it upper more elegantly.
I think the background of the situation needs to be taken into account here. The Met police have quite an abhorrent recent track record for unlawful killings, with a number of high profile cases such as Jean Charles De Menez, Smiley Culture, Steven Lawrence and Ian Tomlinson being played out in the media, and high court, and exposing wide spread, high level police corruption in such cases, and even systematic racism. The Iain Tomlinson case especially, is chilling to read about http://en.wikipedia.org/wiki/Death_of_Ian_Tomlinson - and shows the rampant subterfuge which exists in the Met.
Take into account the first news reports that the man shot dead was an armed drug dealer who shot at officers, to the details which we are now seeing, that the IPCC was on the case almost immediately afterwards, the balistics report saying that the bullet fired at the officer was actually from a police issue handgun, and therefore seems to be a colleague who could have misfired, and the heavy handed tactics shown by police during the original, peaceful protest outside the constabulary station
Some of the highest levels of unemplyment in recent years, the disparity in wealth between the "rich" and "poor", political apathy, huge public sector budget cuts, banking and economic crises where the architects aren't ever held accountable, widepspread journalistic and police collusion and corruption by one of the biggest news ocroprations, and a general feeling of disenfranchisement of the youth that are rioting all need to be taken into account. Couple this with channels like MTV showing people who started out in the same situation as many of the kids involved in teh riots boasting about their enormous levels of wealth, a society where immense physical wealth and possesions are lusted after, sports stars making more in a week than most of these people could hope to make in a year and you can start to see where problems could stem from.
Is most of the rioting and looting as a direct result of the killing of Mark Duggan? Probably not. Most of the people involved are probably opportunists, taken an opportunity to get some free swag with no repurcussions, hiding behind a legitimate cause. The fact that theose involved are undoubtadely disenfranchised with their current situation is unarguable though, and this is the bigger picture that society has to deal with to stop this sort of thing happening in the future. People calling for martial law and vigilantism are missing the wider issues which have to be dealt with for a fully functioning society in my opinion.
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I vote Apc's with water cannons on the rioters. There a unruly mob with no purpose but to loot and steal from others. They have no business being there and are using this death as a cover for there own gain. After all anyone who was there orginally to protest is long gone and replaced with these idiots.