I've definitely experienced strong adverse reactions to discussing eugenics 'cavalierly' if you don't spend at least ten to fifteen minutes covering the inferential steps and sanitising the perceived later uses of the concept.
Good point about the possible three communities. I haven't posted here much, as I found myself standing too far outside the concepts whilst I worked my way through the sequences. Regardless of that, the more I read the more I feel I have to learn, especially about patterned thinking and reframes. To a certain extent I see this community as a more scientifically minded Maybe Logic group, when thinking about priors and updating information.
A lot of the transhumanist material have garnered very strong responses from friends though, but I've stocked up on Istvan paperbacks to hopefully disseminate soon.
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.