The Patent Dragon's Zone of Soul Retraction

In The News... "Environmental protestors" have gone to the papers about being approached by the police to become paid informers. The protestors' view is that this is nothing but an attack on their freedom to protest, but I feel compelled to ask this: Can these protest groups guarantee to the country that they haven't been infiltrated by individuals or groups with malicious intent in mind towards this country? It would only take one "green activist" with a rucksack full of Semtex to kill hundreds at Heathrow, or irradiate a big chunk of the country by blowing up crucial equipment at a nuclear power station...

And no, I don't think the terrorists won't be accommodating enough to dress the part, just to make it easy for you.