Because until a group does or plans/encourages something like the Oregon takeover or the Nevada standoff they aren't really much more than a particularly pessimistic neighborhood watch with a penchant for guns and a bit of dress up.
Seizure of government property at gunpoint is certainly something.
(Though I'm not sure it really tracks with the definition of a "terrorist," since a terrorist is an armed combatant who explicitly strikes at civilians instead of at their government. A better term here might be more 19th-century-flavored words like insurrectionary or seditionist, though terms like those fell out of use as rebel and guerrilla groups abandoned direct attacks on governments in favor of terroristic tactics.)
> terrorist is an armed combatant who explicitly strikes at civilians instead of at their government
Uhm, no. This is closer to the definition of terrorism, but it's still not it. Drug store robbery gone violent involves armed people who may explicitly strike a civilian shop owner who turned out to have a gun under the counter.
Terrorism is about intent: to spread terror. If you're blowing a bomb up just to see the bodies fly, you're not a terrorist. But if you're conjuring an alien monster abomination to prevent a nuclear war between two super-powers through _terror_ against an imaginary alien adversary, you are a terrorist (although in this case one could argue that you indeed do it for the greater good).
(5) [T]he term “domestic terrorism” means activities that—
(A) involve acts dangerous to human life that are a
violation of the criminal laws of the United
States or of any State;
(B) appear to be intended—
(i) to intimidate or coerce a civilian population;
(ii) to influence the policy of a government by
intimidation or coercion; or
(iii) to affect the conduct of a government by mass
destruction, assassination, or kidnapping;
and
(C) occur primarily within the territorial
jurisdiction of the United States.
How is the Malheur occupation not domestic terrorism, under that definition?
Calling someone a "terrorist" only when they've engaged in "terrorist activity" is circular reasoning. I'd wager the GP's point is that defining what makes a "terrorist" is all in the eye of the beholder. The tone of the posted article avoids using words ("terror" words) that are quite readily used when other demographics engage in similar behavior.