While many people believe the police have not come down on rioters hard enough, this video below shows police in Manchester beating a group of alleged rioters without provocation:
We don't really know the context of the assault above, but the police should only resort to force if they are directly threatened. It appears that in this case, the police took the fight to the rioters (and there's no proof they are rioters) and gave several of them a nasty beating.
I understand that the police have an incredibly difficult job, but this type of behavior is unacceptable and should not be tolerated under any circumstance.
I have heard from many young people in London about police brutality and random searching, and if true, their resentment is entirely understandable. Most white middle class people have no idea what it is like to be continually harassed and suspected of being a criminal, and it is difficult for them to understand why there is such animosity towards the police from certain social and ethnic groups.
The video above gives insight into the type of justice underprivileged youths are subjected to.
In their world, they are guilty before being proved innocent.