That’s why he put in the 2/3 majority to change the rates.
Originally he wanted to repeal the 16th first, but after talking to economists, he adjusted it so that there would be some time to cut government spending/programs, bring the debt down, educate people so they will pressure Congress to pass HR25 (Fair Tax)
But how is the 2/3 super-majority enacted? Because if you pass a law or make a rule that Congress must have 2/3 super-majority to pass a tax increase, Congress could simply have a majority vote to change the law or rule, then have a majority vote to increase taxes.