I voted NO, because the filth should already have the powers to arrest someone for making a nuiscance of themselves/setting fires in a public place. Demonstrating is one thing, causing a 'danger to the public' by starting a fire
should be considered another entirely.
Imagine if I were to go into the middle of town and start a fire in a rubbish bin, or take some wadds of paper/combustible material and then proceed to set it alight... I would imagine the powers that be would be none too pleased. The same attitude should apply to the burning of flags in a public place. The only real difference here seems to be if you do it alone you'll probably get nicked, but if you're in a crowd then you have the safety in numbers to do whatever the hell you want
If flag burning is your thing then go to some armpit type country where that kind of thing is the accepted norm and forte for your average illiterate fannatic. See? Everyone has a niche somewhere to fit in, it just so happens that with any luck that niche is way out in the back of beyond, far away from Blighty.