Was Hitler objectively bad?

[Edwardo Piet]

There is none. I keep making this distinction because every time you ask why I 'ought', I give you an 'if', and each time you say something nonsense like "that's not objectively prescribing it's self".

Can you name me something that objectively prescribes it's self?

I meant that it can't prove that it objectively should be followed. It's objectively descriptive but not objectively prescriptive.

'Objective morality' simply requires that the moral propositions are objectively true or false.

So yes Desirism is objective in the sense its descriptive propositions are true.

Of course not, we have no IF in your example. It's the same fundamentally flawed objection you bring up time and time again, the necessity for intrinsic value. If scientists want to know about X they ought to do what they believe will best lead to knowledge about x.

And so science is based around objective ideas about nature and the universe and whatnot so in that sense it's objective. But it still can't objectively prove itself as true without tautology because there are only tentative truths like you say, so in that sense it's not objective.

The difference is science is descriptive only. It doesn't attempt to bridge the 'is' 'ought' gap.
It is true that if you can't value 'X' then it makes no sense to say you should value it. But if you can value 'X' there is nothing to say you 'ought to' value it.

And what we ought to do is a relationship between what we desire and what actions will get us to a state of affairs in which the desire is true.

You can't prove that, you can only assume it. The fact that we can desire 'X' doesn't objectively mean we should fulfil that desire even if it's to the fulfilment to all desires of everyone.. That's just your own judgement that 'better for everyone' is better, that goes past describing and into prescribing. You haven't bridged the 'is' 'ought' gap.

It's Descriptive in it describes a relationship between a set of desires and a state of affairs

Yes it objectively does that.

It's Prescriptive in that it prescribes the action that tends towards said state of affairs.

No it doesn't do that objectively.

Prescriptions are reasons for action,

No, prescriptions say we "should" act whether that's true or false (and I don't see how that can be objectively true or false at all). 'Reasons for action' (desires) merely say why we already act not that we should act, they are descriptions only.

desires are the only reasons for action that exist. If you want to tell someone you ought to do x, you are saying they ought to have the desires give you reason for action to do x.

You are describing the obvious fact that it makes no sense to tell someone that they 'ought' to do 'X' if they can't, and they can't if they don't have the reasons for action (desires) to do so. But you still don't objectively show whatsoever that they ought to do anything at all. You haven't bridged the 'is' 'ought' gap. You don't objectively prescribe at all you just objectively describe and then sneak the subjective prescription in.