The homepage says:
Less Wrong is an online community for people who want to apply the discovery of biases like the conjunction fallacy, the affect heuristic, and scope insensitivity in order to fix their own thinking.
Less Wrong users aim to develop accurate predictive models of the world, and change their mind when they find evidence disconfirming those models, instead of being able to explain anything.
So this person acknowledges their own biases, notes that some otherwise perfectly reasonable and in their opinion "Rational" people believe in HBD, and then (as far as I can tell) doesn't make any effort to investigate whether they might actually be true?
This is what motivated cognition looks like. If someone cannot change their mind because (sorry for the bluntness but there's no other way I can describe my impression in under a paragraph) their feelings might be hurt, and they are actively working against resolving this inner conflict, then they should not be in a rationalist community.
It's not clear to me that avowed racists (and sorry, that's what "HBD" is a euphemism for) make up any any significant portion of the LessWrong community, just a loud portion of it. Self-described "reactionaries" are certainly a very small (but loud) minority here.
Really we should get better at conveying when opinions held by a loud minority here are not by any means the opinion of the majority.
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.