UPB in an eye dropper

Here is my attempt to make the shortest possible summary of UPB:

When someone makes a moral claim, when they use a sentence with the words "ought," or "must," or "should,"¹ if their proposition doesn't apply to all moral agents, everywhere, for all time, then that person is a hypocrite and you can ignore their bogus claim. If it does apply universally, you need to take it seriously, but it shouldn't have logical contradictions or practical impossibilities.

Where do the moral propositions come from? We do not derive them from the theory, we just apply the tests to claims we hear or devise ourselves. From this perspective, UPB is just a method we use to test any sort of proposition. If it fails the test, it is either not a moral proposition or it is not true. If it passes, it is a true moral proposition. Stef claims that a surprising number of conventional moral theories fail the test, containing some sort of special pleading or performative contradiction of the norms of argumentation. 

Of course, a skeptic can still dispute Stef's conception of what argument actually presupposes. What argument does Stef present to support his idea of strong universality? Is it possible that moral propositions that pass the UPB test could contradict each other? I'm not sure how to answer those questions, but I want to think about them and others. If you have suggestions, please add them to the comments section.

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 1 Sometimes we use these words to show a logical or practical necessity, rather than a moral necessity. UPB only applies to moral propositions. I wanted this summary to be short, but still reasonably clear. I hope that helps.  ^↩