Agree McG.

For my own part I would probably not have the guts to respond with violence even if relatives of mine were caught up in the collateral.
And who would you chop up if you did have the guts?
A young soldier with a loving wife and kid?
A police man or woman?
It should be obvious to anyone that such a monstrous crime would provoke at least a few people to violence
Again, against who?

And you are in Cloud Cuckoo land if you think the present level of terrorist threat is unrelated to US and UK interference in Iraq and Afghanistan.
It maybe this time.
And if they do it because we allow gay marriage or women's rights, should we go back on that?
We are live in a democracy. Not by luck but by bloody sacrifice.
When a government ignores our will we throw them out.
We do not chop up helpless, unarmed young squaddies and pretend we are doing something noble.