I would agree that the main problem is a lack of clear truth conditions for "x sucks;" the fact that it's a claim about subjective states, and that it relies on implicature, is immaterial. But this is a problem to some extent for nearly all natural-language terms, including "x is rational" in the colloquial sense. And the problem can be resolved by stipulating truth-conditions for "x sucks" just as easily as for "x is rational." So I think we'd agree that we should focus on getting people to taboo and clarify all their words, not just on feigning 'objectivity' by avoiding making any appeals to preferences or other mental states. Preferences are real.