I'm looking forward to the give and take, so out of impatience I'm going to add another question. In return I'll give a rough idea of where I am concerning racism. From a different area of the comments:
But if anyone here thinks that academia is less open and diverse now than it was 50 years ago, please recommend a source.
You can change the "and" to an "or", if you like. I'm interested if you would say something like, "no, but significantly less open than it would have been were it not for X." We might agree.
Racism: I'd make some boilerplate noises about inherent tribalism and group psychology as general background. Then I'd make some more boilerplate noises about the particulars of racial history in America. For the conceptual work, I would avoid any bother with necessary and sufficient conditions and go straight to fuzzy categories and representatives, along with some type distinctions. As a Less Wrong resident, you should know why I'd prefer this approach to what non-nerds typically do when asked what they mean by something: try to give a precise definition. If you try to do that, you'll probably include some true things that should be believed and doesn't make you a racist in any significant sense. For example, "judging people by the color of their skin." That's a terrible definition, but I bet it's a common answer. I can very accurately infer quite a lot about a person using skin color. When I meet a Korean or American-Korean, I've met something locally rare: somebody who knows what I mean when I say I watch professional Starcraft.
So which elements of this fuzzy category do you consider "false and nasty". For example, what do you think of John Derbyshire?
Related: Heuristics for Evaluating the Soundness of the Academic Mainstream, Admitting to Bias, The Ideological Turing Test