Thus we see the basis for the rationale given in the Copyright Clause itself: “to promote the progress of science and the useful arts,” which is very different from creating some kind of entitlement to creators because they “deserve” it.

... You realize the reason it promotes progress is because it allows the creators to get paid for it, right? It's not "they deserve it" it's "they need to eat and thus they aren't going to do it unless they make money." Which is exactly my argument.

Ownership of property is a natural right which the Constitution pledges to protect (see also the 4th and 5th Amendments), but the temporary monopoly called copyright is merely a privilege granted at the pleasure of Congress

It's a silly way to put that since the "privilege granted" is given in to Congress in the Constitution.

Overall though, you are referencing a 300-year-old document like it means something. The point comes down to people needing to eat in a capitalistic society.

This is a bizarre, backwards argument. First of all, a government-granted monopoly is the antethesis of the “free market” upon which capitalism is supposedly based.

Capitalism isn't really based on a free market and never has been in practice.

Second, granting of monopolies is hardly the only way to accomplish either goal of “promoting the progress of science and the useful arts” or of helping creators make a living!

Sure but first enact those changes then try to change or break copyright. Don't take away the only current way for artists to make money then say "Well, the system should be different." You are causing people to starve at that point.