Of course the terrorist-excusers like to make out that it was just a bit of paint, what's the issue? It was 7 million pounds of damage (to be paid for out of our defence budget, so that's 7 million quid less to spend on other things) and put some of our key national defence infra out of commission for a period to boot.
But of course, that's ok - we should allow such groups to exist going around attacking people, crippling them and destroying national infrastructure to the tune of millions, its just free speech innit.
No sensible country in the world would allow such groups to exist.