Every once in a while I need a reminder of why I am not a liberal “progressive,” and this kind of thinking went a long way:

…members of the movement Right demand that their candidates buy into the Entire Package of Wingnuttia. This isn’t simply political purism, it’s about validating a worldview. There are all these articles of faith in wingnuttia which have been given to them by the wingnut noise machine, and failure to embrace them all is a signal that you aren’t really part of the club.

My first reaction was that the wording could (with very little effort) be changed around to reflect the other side:

….members of the movement Left demand that their candidates buy into the Entire Package of Moonbattia. This isn’t simply political purism, it’s about validating a worldview. There are all these articles of faith in moonbattia which have been given to them by the moonbat noise machine, and failure to embrace them all is a signal that you aren’t really part of the club.

Being dutiful enough to at least click on Atrios’s link, I found this warning to Republicans:

I’ll end with one stat that ought to worry any Republicans who think sticking with the Rove strategy is a good idea. According to the Pew study, members of Gen Y (18-30) are about as likely to be atheists/agnostics (19 per cent) as Republicans (no age group breakdown, but it must be less than the 25 per cent for all voters given low party identification in this age group).

The operating assumption seems to be that if you don’t agree with us on everything, you are not part of our club. (Republicans do not allow atheists and agnostics, at least according to the left. And if they do, they are hypocrites!)
The overall phenomenon reminds me of Ann Althouse’s now classic observation:

bloggers on the right link to you when they agree and ignore the disagreements, and the bloggers on the left link only for the things they disagree with, to denounce you with short posts saying you’re evil/stupid/crazy, and don’t even seem to notice all the times you’ve written posts that take their side.

To which a reader emailed:

…the Right is looking for converts and the Left is looking for heretics…

And who will be nicer to the doubters who are deemed heretics by one side but stop short of being converts to other?
This recent post by Ann Althouse reminded me that the issue is far from settled. Some libertarians seem a little too impatient with unconverted heretics — as if they’re a little too convinced they’re right.
On the other hand, if you’re not 100% convinced you’re right, most of the “isms” are best avoided.