Good point - I changed the title of the document. (I'm letting "the Scary Idea" remain in the topic of this post, so that people can quickly see what this thread is about.)
I think 'scary idea' is a very appropriate description. At the same time many would try to hide up the fact that idea is scary, to appear more rational and less rationalizing. The scary stuff does not tend to result in most sensible reasoning - look at war on terror spending vs spending those money on any other form of death prevention.
edit: that is to say, the scary ideas, given our biases when scared, need lower prior for validity of reasoning. People try to get others to assign higher prior to their ideas than would be reasonable, by disguising the mechanism of arrival at the idea.
Here's my draft document Concepts are Difficult, and Unfriendliness is the Default. (Google Docs, commenting enabled.) Despite the name, it's still informal and would need a lot more references, but it could be written up to a proper paper if people felt that the reasoning was solid.
Here's my introduction:
And here's my conclusion:
For the actual argumentation defending the various premises, see the linked document. I have a feeling that there are still several conceptual distinctions that I should be making but am not, but I figured that the easiest way to find the problems would be to have people tell me what points they find unclear or disagreeable.