I agree, and while I wouldn't describe the Tea Party as radicals, I think the author's point is that they aren't conservative by any traditional definition either. That's why they separate "traditional conservative" from Tea Party (that they then describe as "radical conservative). Maybe this is a case where a great word with a pre-established definition doesn't really exist.
The word you're looking for is reactionary. People, in conversation, may misuse words, invent new phrases to describe something they're thinking of, or even use words which mean the opposite of what they intended, but writers, public speakers, and people who wish to discuss things meaningfully should do better. It's really sad the way journalists will just parrot the PR that comes from political organizations and commercial interests, who are frequently misusing language deliberately to advance an agenda. Journalists are professional writers. They should know better.Maybe this is a case where a great word with a pre-established definition doesn't really exist.