You clearly havent thought too hard about it. How is it perjorative to suggest it's an impossible task to find a balance? If you read my comment more carefully and think a little harder about it you'd spot that I'm ambivolent. 

I quite agree taking these events as examples, I also accept that the Madrid bombings make a poor case for ID cards. However there have been a stream of planned attacks which have been prevented. Though taking your sceptical view these are all of course fiction.

Edited to link to this