I've only read what is posted here and about half (maybe) of the post at SASS, but I noticed in a couple places she talks about having a goal of hating "everyone." She mentions it specifically in the section labeled "Fat is not you Enemy" and notes that she had been reading fat acceptance blogs as fuel, basically, toward her goal of total misanthropy.

So it doesn't seem to necessarily be ignorance OR stupidity - it seems like she's just a very miserable person who has a need to hate everyone.

NOTE: I am NOT defending her - what she did was horrible, and why she did it is not really the point. I just thought, though, that it might be good to throw that info in to the discussion of her motivations, since that's the one she ascribes to herself.