The Big Lie is that a woman is paid only 72% of what a man is paid, with the implication (or, sometimes, the outright claim) that they are doing the exact same job. That violates a very basic law of economics. If a business owner or department manager could get a job performed by a woman for $72,000 instead of paying a man $100,000, he (or SHE) would hire the woman every time.
With minor exceptions, equal work for equal pay is already a reality in the U.S.