It informs the debate in the sense that it confirms music does have value. It's sophistic to claim that music has no value because people can avoid paying for it, which is I think the point your parent was trying to make.

We have to make sure that we do not conflate utility (absolute value) with market value.

Yes, market value is probably not the term we want to use to make statements about what should be done around copyright law. Anything you can't force people to pay for has no market value. Making a normative statement about whether people should have to pay for something based on market value is begging the question.

It's more important to think about utility, because that can help us answer the question of whether the government and laws should be used to create market value where there is none by trying to make a good excludable.