Just imagine that you would have a certain proof (by observing parallel universes, or by simulations done by superhuman AI) that e.g. a tolerance of homosexuality inevitably leads to a destruction of civilization, or that every civilization that invents nanotechnology inevitably destroys itself in nanotechnological wars unless the whole planet is united under rule of the communist party. If you had a good reason to believe these models, what would your values make you do?
Perfect information scenarios are useful in clarifying some cases, I suppose (and lets go with the non-humanity destroying option every time) but I don't find them to map too closely to actual situations.
I'm not sure I can aptly articulate by intuition here. By differences in values, I don't really think people will differ so much as to have much difference in terminal values should they each make a list of everything they would want in a perfect world (barring outliers). But the relative weights that people place on them, while differing only slightly, may end up suggesting quite different policy proposals, especially in a world of imperfect information, even if each is interested in using reason.
But I'll concede that some ideologies are much more comfortable with more utilitarian analysis versus more rigid imperatives that are more likely to yield consistent results.
A long blog post explains why the author, a feminist, is not comfortable with the rationalist community despite thinking it is "super cool and interesting". It's directed specifically at Yvain, but it's probably general enough to be of some interest here.
http://apophemi.wordpress.com/2014/01/04/why-im-not-on-the-rationalist-masterlist/
I'm not sure if I can summarize this fairly but the main thrust seems to be that we are overly willing to entertain offensive/taboo/hurtful ideas and this drives off many types of people. Here's a quote:
The author perceives a link between LW type open discourse and danger to minority groups. I'm not sure whether that's true or not. Take race. Many LWers are willing to entertain ideas about the existence and possible importance of average group differences in psychological traits. So, maybe LWers are racists. But they're racists who continually obsess over optimizing their philanthropic contributions to African charities. So, maybe not racists in a dangerous way?
An overly rosy view, perhaps, and I don't want to deny the reality of the blogger's experience. Clearly, the person is intelligent and attracted to some aspects of LW discourse while turned off by other aspects.