"Any of the objectors up above have any suggestions as to how the police and security services should gather intelligence of the activities of extremists who plan to do the rest of the population harm?"
Right on cue Terribus (right being the operative word)!
The police and security authorities are there to uphold the law - not to decide in advance who the criminals are (or might be) - we have courts for that.
The police in particular have proved themselves in the past, to be more than happy to deny the rest of us our lawful rights - the miners strike more than proved that. There, they put themselves totally at the disposal of one of the most repressive national leaders in modern history - Margaret Thatcher, a prime minister who supported, openly admired and counted as a friend one of history's monsters, Augusto Pinochet, mass murderer and torturer.
Putting the powers of surveillence of the rest of us into the hands of such a force is not only detrimental to our own well-being, but also is a pretty positive step along the road of he extremism and repression - in other words, it becomes as extreme and repressive as the terrorists we are supposed to be fighting.
Since when have legally held political demonstrations and protests been subversive and subject to surveillence, or are you suggesting that our law-makers have it wrong and the police should decide what is or is not permissable?
Jim Carroll