Alan Simpson let loose at a group of Californians who charged in a brochure that he and Erskine Bowles were “using the deficit to gut our Social Security.” The former Republican senator from Wyoming sent the California Association of Retired Americans a characteristically colorful response, which I quote: “What a wretched group of seniors you must be to use the faces of the very people (the young) that we are trying to save, while the ‘greedy geezers’ like you use them as a tool and a front for your nefarious bunch of crap.”

I can’t not like Simpson, but he is wrong this time, and the activists are right. The plan named for him and former Clinton Chief of Staff Bowles bravely confronted soaring deficits with balanced spending cuts and tax hikes. Upon its release, the tax-a-phobic Grover Norquist called Simpson “old and grumpy.” Simpson fired back with “old Grover Norquist and his happy band of goofy warriors, all they do is make money off of people.” And I, too, have made past reference to “greedy geezers.”

But Simpson-Bowles had no business dragging Social Security into the operating room, and here’s why: Social Security is an independent, self-funding program. It is not welfare. The workers and their employers pay for all of it.

About 25 years ago, Social Security taxes were raised above that needed to support current retirees and the surplus put in a trust fund. The goal was to create a buffer to keep the program healthy as the number of retirees grew and lived longer. Left alone, Social Security can pay all promised benefits for the next 20 years, and can continue doing so with some minor adjustments, such as raising the cap on income subject to payroll taxes.

Conservatives and “centrists” who call for compromise on the Social Security Trust Fund still don’t get it, so let’s bang the gong again: The trust fund represents real money taken out of workers’ pockets, and the money it loaned the Treasury is really owed.

Simpson-Bowles did fine calling for a curb on projected entitlement spending. That, of course, includes Medicare, the health-insurance plan for the elderly. Unlike Social Security, Medicare is not self-supporting. Medicare payroll taxes and payments by beneficiaries cover only some of it.

The Social Security Trust Fund is a big piece of change, and by declaring the Treasury securities sitting in it “worthless pieces of paper,” our right-wing politicians can throw the obligations overboard in the service of more tax cuts for the rich — with the added bonus of killing off a program they never liked much. Often citing some scuzzy accounting methods applied to the surplus, they tell us, “Whoops, the money has been spent.”

Well, duh, all the money the Treasury borrows has been spent. That’s why it borrows money. Every bond it issues to investors across the globe represents a debt. And if the Treasury hadn’t been able to borrow that money from the trust fund, it would have had to borrow more from the public.

Then-Federal Reserve Chairman Alan Greenspan was asked in 2001 whether the trust fund investments were real or not. His response: “The crucial question: Are they ultimate claims on real resources? And the answer is yes.”

The California Association of Retired Americans was overenthusiastic but correct in its assertion that Simpson-Bowles envisioned using Social Security to balance budgets that the program is not supposed to be part of. They were perhaps unfair to imply that the intention was to gut Social Security. Some politicians might like that, but the more realistic explanation is that many simply don’t know what they’re doing.

Froma Harrop is a Providence Journal columnist. Her email address is fharrop@projo.com.