Unknown: If Robin is right, then Eliezer is against overcoming bias in principle, since this would be taking an outside view (according to Robin's understanding)

I thought that overcoming bias was about reaching true beliefs, not adhering to some particular ritual like using outside views.

Bayes' Theorem says that P(H|DI) is proportional to p(H|I) * p(D|HI), where D is the data, H is the hypothesis, and I is our background information. A common mistaken intuition is that P(H|DI) = p(D|HI). The "outside view" seems to be that p(H|DI) = p(H|I). This is just plain wrong. As Eli states above, by varying your choice of D' and I' such that D'I' = DI, you can make p(H|D'I') equal to all sorts of things by using the outside view heuristic. Getting good predictions from the outside view requires you to have good intuitions about what to use as D and what to use as I.

Having useful approximations is great. Turning a useful approximation into your new definition of rationality is a bad, bad idea. You say that Robin thinks that overcoming bias means taking outside views. I think Robin knows better than that.