Re: Pragmatism
I have never "screamed" that the police/security services should have prevented a terrorist* attack. All the successful attacks would have required unacceptable levels of intrusion into everyone else's life in order to get the information that might** have led to the act being prevented. Too many people with no intention of causing harm would be (are) surveilled based on what websites they visit, and it is far better that one person who wants to cause harm should do it than ten (thousand) people who don't come under suspicion.
However, this applies only to comms surveillance. If the police/security services had the information due to physical evidence leading to targeted surveillance and they did nothing, then I would want them hanged, drawn and quartered.
*The word is horribly abused, and the actual risk of it is trivial, but I'll go with it for now.
**There is only a small likelihood that any information would have led to action, at least because of the sheer amount of noise generated by the amount of surveillance required.