Standing up for supervenience

There is a well-known argument against irreducibly normative properties that appeals to the following claim about supervenience: for all possible worlds W and W*, if the instantiation of descriptive properties in W and W* is exactly the same, then the instantiation of normative properties in W and W* is also exactly the same. This claim used to be uncontroversial, but recently several philosophers have challenged it. Do these challenges undermine this argument? I argue that they do not, since the negation of this claim about supervenience has consequences that are much more implausible than the negations of key premises in these challenges.