A current thought experiment I'm pondering:
Scientists discover evidence that popularly discriminated against really does have all the claimed negative traits. The evidence is so convincing that everyone who hears it instantly agrees this is the case.
If you want to picture a group, I suggest the discovery that Less Wrong readers are evil megalomaniacs who want to turn you into paperclips.
How, if at all, does this affect your ideas of equality? Is it now okay to discriminate against them? Treat them differently legally? Not invite them to dinner?
I've heard Peter Singer says useful and interesting things about this, but it hasn't yet reached the top of my bookqueue.
The practice in the US of alerting people in the neighbourhood to the presence of convicted child molesters (or was it rapists? I don't remember) seems to indicate that at least some people think that it's a great idea. I think that as we get better at testing people for sociopathy we're likely to move towards certain types of legal discrimination towards them too.
None of this affects my personal ideas of equality though. I would prefer not to be friends with an evil megalomaniac in the same way that I would prefer not to be friends with a drug addict, but if I met an interesting person and then discovered that they were an evil megalomaniacal drug addict I wouldn't necessarily cut them out of my life, either.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
(I plan to make these threads from now on. Downvote if you disapprove. If I miss one, feel free to do it yourself.)