What's contradictory about the same object being judged differently by different standards?

Nothing. There's nothing contradictory about multiple subjective truths or about multiple opinions, or about a single objective truth. But there is a contradiction in multiple objective truths about morality, as I said.

Here's a standard: return the width of the object in meters. Here's another: return the number of wavelengths of blue light that make up the width of the object. And another: return the number of electrons in the object.

There isn't any contradiction in multiple objective truths about different things; but the original hypothesis was multiple objective truths about the same thing, ie the morality of an action. If you are going to say that John-morality and Mary-morality are different things, that is effectively conceding that they are subjective.