Six years into Obamacare, its critics still see the Affordable Care Act as a sign of the apocalypse. All three Republican candidates for president have vowed to repeal it if elected. Their obstinacy is a reminder of past naysayers who similarly predicted that Social Security and Medicare would destroy the fabric of America.

Actor and budding politician Ronald Reagan, in a speech recorded in 1961 for the American Medical Association, called Medicare "socialized medicine." Were Medicare to become law, he said, "One of these days, you and I are going to spend our sunset years telling our children and our children's children what it was once like in America when men were free."

Sen. Barry Goldwater took just as dim a view of Medicare in 1964. "Having given our pensioners their medical care in kind, why not food baskets?" he asked. "Why not public housing accommodations, why not vacation resorts, why not a ration of cigarettes for those who smoke and of beer for those who drink?"

Medicare began as an amendment to the Social Security Act, which millions of retired seniors with meager pensions, or none at all, depend on today to survive. But in the 1936 presidential election, Republican candidate Alf Landon said financing Social Security through payroll taxes was a "cruel hoax" and a "fraud on the working man."

Just think what the condition of the millions of seniors who depend on Social Security and Medicare would be today without the federal health insurance and retirement savings programs. Social Security and Medicare were never perfect, and future reforms may be inevitable, but that won't require shutting down the programs.

Nor does Obamacare have to be killed to cure its warts. Critics with ulterior motives, including White House aspirants who think their interests are best served by denigrating anything President Obama proposes - including his nominee to the Supreme Court - won't acknowledge that the ACA, flaws and all, has made a positive impact in its first six years.

Up to 20 million Americans who had no health insurance before Obamacare, including four million benefiting from state Medicaid expansions, now have medical coverage. Insurance companies can no longer deny coverage of previously existing illnesses. Struggling young adults up to age 26 can stay on their parents' insurance policies.

Much of the criticism of Obamacare comes from free-market groups supported by health-care providers. But while some people have been genuinely hurt by the law's provisions, much of their pain can be eased if Obamacare's flaws are fixed, insurance companies get better control of their costs, and self-serving politicians stop their moaning.