There was a question and brief discussion about the Union flag issue that is at the root of this at:
http://www.theanswerbank.co.uk/News/Question1195736.html
Just to recap in case anyone doesn't know, the Union flag used to fly 365 days a year on the majestic City Hall. but there was a bid by Nationalists on Belfast City Council to ban it completely. The Alliance Party enginered a compromise motion which would see the flag flown on special occasions only (actually, and somewhat ironically, bringing Belfast in line with the rest of the UK). This motion was passed. Since then loyalists have been protesting in various places, mainly Belfast.
Of course the violence is completely unjustified. There have also been attacks on the homes and cars of Alliance Party, Unionist and Nationalist politicians alike. It's likely some of these have been by Republicans.
When you get violence like this in Loyalist areas you can be 99% certain it's being orchestrated by paramilitaries, exploiting the grievances of gullible people for their own ends.