I meant what I said about not wanting to continue the conversation, but since you're asking me questions, I'll give you (some) answers. I hope you won't hold it against me if I don't answer further questions, though.
What moral theory are you using to make this judgement?
None. I don't think morality admits of theoretical systematization. I'm sympathetic to moral particularism.
Is someone who believes group X has lower average IQ, for example, then group Y a racist?
No. I believe there are differences in average IQ between racial groups, and I don't consider myself a racist.
Derbyshire's belief in racial IQ differences is not why I think he's a racist. It's things like advising his children not to assist black people in distress, and offering as a reason a single news story about some black people who killed a man who was helping one of them. Or advising his children not to go to an event where there will be a large number of black people, and offering as support a single news story about a shooting at an event with a large number of black people. Or asserting without evidence that 5% of all black people are ferociously hostile to whites and will go to great lengths to harm them, and that 50% of blacks will passively go along with this 5%. Or saying that one should scrutinize a black candidate for political office much more carefully than a white candidate. These are all claims he makes in the column that got him fired.
No. I believe there are differences in average IQ between racial groups, and I don't consider myself a racist.
Well that's a start. What about differences in propensity to commit violent crimes?
Near as I can tell, your complaint about Derbyshire is that he takes the implications of this difference seriously and is willing to openly say so.
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.