If we were living in the colonial days, only the British would be calling them "radical" or "extremists". :D

Men of authority pledging not to bow to unconstitutional orders against citizens. Actually seems noble.

I suspect they get the "radical" and "extremist" label from our culture where those who aren't on the "correct" political side are labeled a Nazi or Communist.

It's more the rampant racism, conspiracy theorism, and calls to violence. Ironically their leadership engages in both of the labeling behaviors of which you complain. This is all documented in the link SauciestGNU provided.

There are only 2577 words on that page you linked, and most of them talk about the oathkeepers protecting businesses in Fergusson, the oathkeepers forming a buffer around the Malheur protestors in Oregon, and the oathkeepers responding to the Bundy and Oregon gold miner situations.

You did not read your own link, or you are putting all your eggs on the "McCain is a traitor" quote, which since McCain is a republican, you should love, and the Hilary rant about house to house confiscation of guns, which she has never outright advocated publicly, but has strongly suggested in speeches. That quote may be a bit paranoid, which is why it was selected from thousands of quotes to be included on that web page.

EDIT: Sorry, but there are a pretty small universe of reasons for your dislike on the page linked. I listed them. That's not mind-reading, that's just deduction.

Please don't presume to read my mind.