I feel like you're conflating "unbiased" with "zero-knowledge". Flat-earthism is not an accepted viewpoint here, but that's not because we're biased against flat-earthism, it's just that flat-earthism is stupid. If it turned out that flat-earthers on average were happier and better at getting things done than other people, and if we failed to acknowledge that because flat-earthism is stupid, then that would indicate a harmful bias against flat-earthism.
If the reason we don't debate theism vs. atheism is mere bias, then we're all fooling ourselves terribly. If the reason is that we've thought sensibly about it and come to the conclusion that atheism is correct and the expected benefit of further debate is less than the time and energy costs, then that's okay.
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 a...
Summary: Current social psychology research is probably on average compromised by political bias leftward. Conservative researchers are likely discriminated against in at least this field. More importantly papers and research that does not fit a liberal perspective faces greater barriers and burdens.
An article in the online publication inside higher ed on a survey on anti-conservative bias among social psychologists.
The link above is worth following. The problems that arise remind me of the situation with academic and our own ethics in light of this paper.
I can't help but think that self-assessments are probably too generous. For predictive power of how an individual behaves when the behaviour in question is undesirable, I'm more likely to take their estimate of how "colleagues" behave than their estimate of how they personally do.
This shouldn't be surprising to hear since to quote CharlieSheen: "we even have LW posters who have in academia personally experienced discrimination and harassment because of their right wing politics."
While I can see Lammers' point that this as disturbing from a fairness perspective to people grinding their way through academia and should serve as warning for right wing LessWrong readers working through the system, I find the issue of how this our heavy reliance on academia for our map of reality might lead to us inheriting such distortions of the map of reality much more concerning. Overall in light of this if a widely accepted conclusion from social psychology favours a "right wing" perspective it is more likely to be correct than if no such biases against such perspectives existed. Conclusions that favour "left wing" perspective are also somewhat less likely to be true than if no such biases existed. We should update accordingly.
I also think there are reasons to think we may have similar problems on this site.