Indeed, but the trouble is of course that often the optimal strategy for promoting one's preferences is to convince people that opposing them is somehow objectively wrong and delusional, rather than a matter of a fundamental clash of power and interest. (Which of course typically involves convincing oneself too, since humans tend to be bad at lying and good at sniffing out liars, and they appreciate sincerity a lot.)

That said, one of the main reasons why I find discussions on LW interesting is the unusually high ability of many participants to analyze issues in this regard, i.e. to separate correctly the factual from the normative and preferential. The bad examples where people fail to do so and the discourse breaks down tend to stick out unpleasantly, but overall, I'd say the situation is not at all bad, certainly by any realistic standards for human discourse in general.