That's what I was trying to say in my previous comment. Even if you execute rational reasoning perfectly, if you start with garbage input, you end up with garbage output. If you intrinsically value something horrible, e.g. murdering kittens, rationality isn't going to tell you to not do it; on the contrary, it'll suggest the most effective means of doing that.

> But if your claim is that rationality is independent of culture (which, as I've already noted, is rubbish, since the idea of what is rational and irrational changes with cultural zeitgeist, unless you have some claim to objective rationality which I don't)

I meant it in the same way in which 2+2=4 or F=ma are independent of culture. Of course the work of discovering rational reasoning was happening over long time, with important contributions in Ancient Greece and earlier. But we've only recently managed to get some good formal tools applicable to real-life problems of reasoning, namely probability theory.

> then we can't use a static methods of rationality to judge the goodness of a particular goal, which is obviously context-dependent. So if not rationality, then what? I suggest critical thinking in place.

What do you suggest this "critical thinking" is made of? As for judging the goodness of a particular goal - you can decompose that into parts that can be judged rationally on their effectiveness (and consistency), and parts that have to be judged morally.