At that point, though, you could make the same argument about a rock. Prove that this rock is not conscious.

The context, though, is that Data is both credibly conscious and self aware, and they all know a plausible mechanism for him to have consciousness and self awareness, in a way that's recognizably human in form. The more alien a (supposed) consciousness is, I think the more work you'll have to do in justifying the application of those labels.