People hold different opinions on various things, just as whether or not using water cannons, rubber bullets on rioters in England is a good idea. These measures are considered controversial because they were used in Northern Ireland before against the IRA. I am for using these measures as last resorts. And here is why:
Put aside socio-economic problems or racial issues for now,this is a moral issue. They showed disrespect to their own country and caused fear on the streets. They even provoked the police probably because they thought they were useless, which is partly true because the police couldn't do anything except for "peacekeeping."
Most importantly, they didn't do this because they wanted people to hear their political causes. Riots spread so quickly in London and England because no one stopped them in the first place and the idea of being able to get away with it suddenly popped in these people's mind. "Yeah! Everyone else is doing it, so can I. Nothing happened anyway." This is just like Rodney King in LA back in the 90's again.
The government has to take a harder line upon this issue. Human rights are the last two words I want to hear from them. Spare the rod, spoil the child. Water cannons, rubber bullets or tear gas should be considered as last resorts. They have to learn that these acts come with consequences. They have to learn this lesson sooner or later. Why not start now?