I see nothing wrong with that.
That's fine and dandy until radical enlightenment-era concepts like "Life, liberty, and the pursuit of happiness", "a well-regulated militia as being necessary to the security of a free State", "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures" are considered part of an "extremist belief system". Heaven forbid one advocate violent actions to "advance political, religious, or social change".
It's not like this nation was founded on a (then) extremist belief system, by violent means, to advance political, religious, and social change.
Clearly, there is no place for in modern society for this. We need a law against it. Just like all these right-wing nut jobs armed to the teeth.
Just my take. YMMV
In case you hadn't noticed, we're currently fighting people who crash planes into buildings and think it's perfectly acceptable behavior to saw an innocent person's head off with a dull machete.
I have noticed, but it is also a matter of perspective. Would group of people who crash planes into buildings and think it's perfectly acceptable behavior to saw an innocent person's head off with a dull machete consider themselves radical? Or would they consider a nation who carved out a Jewish nation in their homeland radicals?