Like you, I don't think FIRED have much in common with chronic dolers. But your reasoning is whack.
Society owes the FIRED nothing. Society does not owe the FIRED a 'debt' because the FIRED saved their money instead of pissing it away. You aren't 'calling in societies' debt' when you FIRE. You're making a decision based on your own planning, fortitude, and good fortune.
If anything, the FIRED have a debt to the society which, by its structure and opportunities, allowed the FIRED to become wealthy enough to cease work.
I think you may be misinterpreting me, or perhaps I did not make my point well enough. Let's take two people who get the same salary from age 25 to age 45, and assume their compensation is commensurate with their economic contribution. The spendthrift immediately spends every penny they earn, and the mustachian saves 50%. In other words, the mustachian is deferring their compensation for later. When I say "debt," I am specifically referring to the money the mustachian has saved and invested, because the mustachian can draw on that accumulated wealth to enable themselves to RE at 45. The spendthrift, having spent all their money, has no accumulated wealth, and therefore has nothing to draw on. When both people hit 45, the spendthrift must continue to work, as he has no other source of support. The mustachian, on the other hand, has carefully cultivated his garden of greenbacks to the point where his greenbacks provide enough economic contribution on their own to support him.
Perhaps "debt" was an imprecise term, but it's important to remember that money is a store of economic value, that you can trade for goods or services that you need or want. The mustachian simply defers the redemption of his money for goods and services until he needs them, much like a lender may wait to call a loan due.