How protests can defeat democracy

I'm about to do something I've never done before. I'm about to stick up for the Prime-Minister-before-last Tony Blair. Not for his policies, you understand, and certainly not for his decision to take Britain into the war in Iraq. But for his right to publish his memoirs and, in particular, his right to attend book signings in this country. Believe me, as far as I'm concerned the less we see of Blair on our tv screens the better, but I was appalled that he'd felt forced to cancel two signings because as he'd entered a Dublin bookshop for a signing, protesters had hurled not just abuse, but eggs and shoes too.
I understand and support their desire to protest. But they did nothing for the cause of democracy. Blair pulled the plug on his London events because he was afraid that a similar, or worse, reaction would put innocent members of the public at physical risk and because he was mindful of the potential cost to the public purse of policing what was after all 'only a book signing'.
The protesters may well feel that they've succeeded, but I believe they've failed. This wasn't someone preaching hate or offending public morality. By provoking this decision the protesters haven't only denied members of the public the right to attend, they've silenced their own voices. No signing = no protest. In the UK we live in a wonderful democracy; one that we all tend to take for granted. Our right to peaceful protest is one of the most important aspects of that democracy. But by stepping away from peaceful protest and moving towards physical attacks those Dublin protesters have not only robbed their colleagues of the opportunity to speak out, but robbed the British public the chance to weigh up both sides of the divide.
Protest by all means, rail against what you object to. But don't be self-defeating.