Was Hitler objectively bad?

[theVOID]

Clearly your premises are true, so I think the question is why it should be called morality, unless it is prescriptive in some way. If you are saying that we should act to fulfill the most desires, then that I would call morality. But, as mentioned, it cannot derive an ought from an is, as you admit, which is the meta-ethical difficulty I was referring to. So I don't see how it's any different from various forms of utilitarianism, specifically preference utilitarianism.

I don't think the is ought gap exists under all circumstances, the main problem with most utilirarianism is that the reasons for action come later, in Desirism they come first, because desires are our only oughts we have. Oughts are reasons for action, and the only reasons for action that exist are to fulfil the strongest desire of our conflicting desires.