Of course, that's the whole point. Gotta prevent another Belfast.
In many of the previous riot/anti-immigrant violence cases, those arrested have substantial criminal records, which tends to lead to the "why is this person not in prison already?" discourse.
(look at how long the court system queues are some time. It can be years from offence to conviction!)
Pop quiz: which British journalist was cited as inspiration in the manifesto of Anders Breivik?