"Challenge the status quo" does include "try to get their way politically by resorting to tactics which target civilians in order to cause terror". The animal rights movement certainly has been involved in that kind of "challenge" on a number of occassions. It's not merely a matter of declaring people criminals for having a political goal, but also when they are indeed committing crimes in the name of animal rights or the rights of the unborn or whatever.
Committing a crime does not make one a terrorist. Bombing an abortion clinic should probably qualify you as a terrorist, but theft/vandalism/etc in the furtherance of a political goal is not terrorism. If we do want to redefine terrorism to be this broad, then we really need to reign in all of the extra powers that the government has to go after 'terrorists' because those powers are predicated on the idea that terrorists are using killing people to further their goals.
So, if there are some people who try to "challenge the status quo" by unlawful means, it gives the government the right to harass, spy on, etc. other activists who stay strictly in the bounds of the law? That's exactly the oldest trick in the book - you define the "enemy" so vaguely that soon everyone who doesn't agree with you is a "suspected terrorist" and subject to random harassment or worse.
