I agree with you; I am abusing terminology.
For the record, though, I do think we have a bias against theism in the sense that you’ve described. I understand why LessWrong might choose to consider the “does God exist?” question settled, but we go further than that. We frequently discuss how terrible religion is, and applaud efforts to promote atheism, despite the benefits to happiness etc. that religion provides.
I think it’s understandable that we have such a bias. On LessWrong, we value truth and truth-seeking; this goes far enough that it’s almost a moral value. When other groups actively discourage truth-seeking, we oppose them.
I don’t know anything about social psychology, but my experience with other social sciences suggests that liberal, humanist values are deeply ingrained in their system. What I mean is, the social sciences are not just truth-seeking engines looking for facts about humanity. They have their own moral values attached (e.g. reducing discrimination).
Just as we on LessWrong are reluctant to engage in discussions with people who oppose truth-seeking, social scientists may be reluctant to engage in discussions with conservatives, because conservatives tend to hold moral values that are actively opposed to the social sciences’ agenda.
This article suggests implicitly that the social sciences should be about truth-seeking, not about promoting some political/moral agenda. The willingness of social scientists to admit their bias against conservatives suggest that they feel otherwise.
Our large cryonicist population is probably biasing us towards cryonicist ideas. Our large computer scientist population is almost certainly biasing us towards explanations of consciousness/intelligence which rely on computational metaphors. Our large, outspoken atheist contingent probably biases us away from conveying positive attitudes towards religion, lest we be publicly ridiculed. Are these biases problematic too?
Social groups form based on shared ideas. Of course they will be biased! I think most of us would be unhappy in a totally unbiased LessWrong, because we’d be so busy debating things like theism vs. atheism that we’d have no time to delve into the finer-grained implications of our philosophical worldview.