It is not exactly unprecedented; the FBI and other government agencies have infiltrated and surveilled the Klan, Black Panthers and similar groups for decades. They did it with US Al Qaeda operatives well before 911; my only regret is that better inter-agency coordination would have been prevented 911. The SCOTUS has been very clear there is no First Amendment right to falsely shout, "FIRE!" in a crowded theater.

We are not talking about government surveilling EVERYONE (at least I am not,) only people with documented histories of advocating and/or committing violence. I would certainly never support fishing expeditions through everyones private life, without evidence (e.g. the "USA PATRIOT" Acts warrantless wiretaps.) Yet disputing that "those with nothing to hide have nothing to fear," is not the same as disputing that "those with exposed crimes should be free of scrutiny." It is similar to the difference between saying, "no one should have a gun," and saying, "no one proven a criminal and/or mentally ill should have a gun."