The mind should develop a blind spot whenever a dangerous thought presented itself. The process should be automatic, instinctive. Crimestop, they called it in Newspeak.
He set to work to exercise himself in crimestop. He presented himself with propositions"the Party says the earth is flat", "the party says that ice is heavier than water"and trained himself in not seeing or not understanding the arguments that contradicted them.
George Orwell, 1984 (1948).
The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say which was which.
George Orwell, Animal Farm (1944).
"Tirin wrote a play and put it on, the year after you left. It was funny crazy you know his kind of thing. […] It could seem anti-Odonian, if you were stupid. A lot of people are stupid. There was a fuss. He got reprimanded. Public reprimand. I never saw one before. Everybody comes to your syndicate meeting and tells you off. It used to be how they cut a bossy gang foreman or manager down to size. Now they only use it to tell an individual to stop thinking for himself. It was bad. Tirin couldn't take it. I think it really drove him a bit out of his mind."
Ursula K. LeGuin, The Dispossessed (1974).
Without defending the aspiration to blow up tunnels as appropriate although the purported "plan" wouldn't have worked, it could have killed someone, and might have been revised to something more dangerous the real question is what we're doing to law enforcement authorities. The law enforcement mindset doesn't work very well to prevent crimes; that is, the FBI thinks in the past. And that's what is disturbing here: Not that this particular set of defendants-thoughtcriminals is somehow to be admired for its devotion to righteousness (of some variety), but that this thought process in law enforcement is going elsewhere.
Sometimes easy cases make bad law, or at least bad policy. This could well be one of those times.