Instead, do we decry the legitimacy of the obscurantist's desires? Perhaps, but a convincing argument must be provided for the ethical aspects of such a line of thought
Wait, so now we need "convincing arguments" for our terminal values (edit: which follows from 'we can decry terminal values using convincing arguments')? They need to provide e.g. "societal benefits"? According to whom, or whose standard? What else do we need convincing arguments for, sexual preferences? Or just obscurantism?
No, I do not claim any such thing. To clarify, that statement and the related paragraph assume that there might be grounds for claiming irrational behaviour is to be decried. The reason for this is that a given utility function, with some exceptions, cannot be maximised if its maximiser shuns knowledge as an obscurantist would; this is not generalisable to "sexual preferences" as such, but applies to behaviours conflicting with self-improvement, rationality, preservation of utility functions, prevention of counterfeit utilities, self-protectivene...
Consider the case of an obscurantist i.e. an irrational agent who is proudly ignorant and opposes the spread of (certain) knowledge even to themselves. First of all, is the existence of such an agent implausible? Not really, considering there are masochists out there and that, to some individuals, ignorance is bliss. How much, then, will be left of an obscurantist's identity upon coherently extrapolating their desires? The answers is probably not much, if anything at all.
Do this force us to renounce to the idea of personal CEV? Hardly so. Instead, do we decry the legitimacy of the obscurantist's desires? Perhaps, but a convincing argument must be provided for the ethical aspects of such a line of thought; a utilitarian could draw support from the societal benefits of increased epistemic hygiene in the absence of obscurantists.
In any case, this (admittedly contrived) example illustrates that there are pressing issues regarding CEV and personal identity. Also, on a related note, I recently heard a leading decision theorist say that their greatest concern with Ideal Advisor Theories was how desires become no longer the individuals' but, rather, those of their advisors; it may well be the case that personal CEV incurs in the same issues, at least under the obscurantist's conditions.
The limiting case above also reveals a subtle interplay between knowledge and volition; our desires might (implicitly) involve not wanting to know certain propositions, wanting to not know certain propositions, not wanting to act as if we knew certain propositions, wanting to act as if we did not know certain propositions.
What I just presented is not a rejection of the idea of personal CEV or similar desire-satisfaction theories of well-being, rather it aims to be a pointer to complications one must keep in mind when developing such proposals.