However in case b, wouldn't it allow folks to rationalize themselves as 'not as weird' as perhaps some extreme groups you mention? And then not think about applications of these findings to themselves?

It seems the point of the article was that this issue is a spectrum issue and can trip up folks who may otherwise believe themselves to be approaching something scientifically but in fact have been pre-biased by their emotions on the issue. At least for me (and I do consider myself open minded) it was useful to think about the mechanism behind the 'irrational' response, which certainly could help me in influencing change in organizations where such change would be emotionally difficult.

"I can't figure out what purpose he is serving by exposing only half his readers to the negative emotional reaction, while exposing the other half to the positive emotional reaction that comes from criticizing their political opponents and affirming their already held beliefs. (Unless of course the latter reaction is what he is going for.)"

Perhaps he was going for people to step back and say "Hmm, I'm responding emotionally, let me compare that emotion to whether or not I think his point valid, and how my emotions influenced that thinking." Sort of a step outside your own complexes kind of thing.