Surely if there is evidence of you having committed a crime then you should be charged with it. Planning terrorist attacks is a crime, holding certain beliefs is not. As it happens I'm not terribly keen on the concept of the nation state, it tends to cause wars, so in that sense I'm opposed to the UK. Excuse me if I don't go and hand myself in to the police.

As to your last point, a cynic would say that keeping fear of terrorism high is an excellent method of controlling the population. Not that I'm a cynic...