There would likely be more intellectual diversity among a demographically diverse group randomly selected from the general population than there would be among a homogenous group randomly selected from one demographic within that population. However, if the demographically homogenous group was comprised of specialists of diverse fields of study, they would likely be more intellectually diverse than the demographically diverse group selected from the general population.
What I said was, "There is likely to be more intellectual diversity between an exclusively middle class white male group comprising a physicist, a lawyer, a mathematician, a programmer, a chemist, a politician, an economist, and a businessman than there is between a demographically diverse group of eight people randomly selected from the general population." Please pay attention to the bits in bold.
And the qualities of supporting the left or right are not binaries, they are things that come in degrees, like a thing being hot or cold. When I say, "women support the left and men do not," I mean that more women than men support the left and more men than women support the right. Taken completely out of context, I suppose "women support the left and men do not" could indicate that I meant every woman supports the left and every man supports the right, but that is obvious nonsense. You are twisting my words to fit the most absurd possible interpretation.
A long blog post explains why the author, a feminist, is not comfortable with the rationalist community despite thinking it is "super cool and interesting". It's directed specifically at Yvain, but it's probably general enough to be of some interest here.
http://apophemi.wordpress.com/2014/01/04/why-im-not-on-the-rationalist-masterlist/
I'm not sure if I can summarize this fairly but the main thrust seems to be that we are overly willing to entertain offensive/taboo/hurtful ideas and this drives off many types of people. Here's a quote:
The author perceives a link between LW type open discourse and danger to minority groups. I'm not sure whether that's true or not. Take race. Many LWers are willing to entertain ideas about the existence and possible importance of average group differences in psychological traits. So, maybe LWers are racists. But they're racists who continually obsess over optimizing their philanthropic contributions to African charities. So, maybe not racists in a dangerous way?
An overly rosy view, perhaps, and I don't want to deny the reality of the blogger's experience. Clearly, the person is intelligent and attracted to some aspects of LW discourse while turned off by other aspects.