To maximize open discourse, you have to close down discourse against open discourse.
It's just Marcuse's paradox (which I'm pretty sure I'm coining here): to maximize tolerance, you have to be intolerant toward intolerance. Or in the legal arena: "the Constitution is not a suicide pact."
There are two arguments in that post: "certain elements within the rationality thing signal more than is necessary", the correction of which would aid the goal of generating high-quality open discourse, and "certain conclusions should not even be considered, certain arguments should not be made, no matter their strength, because certain people have memetic immune reactions to them that drive them away from participating at all", the correction of which would mean an end to open discourse. Given that ThrustVectoring (presumably) values open discourse, the response of "I don't even want to discuss anything from that direction" is exactly correct.
That doesn't mean that it can't be discussed, of course; it just means that a community that values open discourse can't discuss it. If apophemi wants there to be a community based around limited rationality -- that is, rationality-minus-discourse-about-certain-things -- well, one can always be started. Secession is always an option, and online, you don't even have to figure out how to build a seastead to secede.
"the Constitution is not a suicide pact."
Humorous, off-topic response: But the Declaration of Independence is!
And for the support of this Declaration, with a firm reliance on the protection of divine Providence, we mutually pledge to each other our Lives, our Fortunes and our sacred Honor.
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.