Umm, it is not the fair taxers who use the 'fairness' rhetoric? The whole way the fair tax is spun and marketed is right out of liberal focus grouping sprinkled with a bunch of overpromises.
Certainly NOT the sort of "from each according to his ability to each according to his need" sort of "fairness" that Marx and Engles proclaimed in their Manifesto, which btw is the genesis of the modern progressive income tax. That is what liberals love. The ability of the government to use the tax system as a social engineering tool to reward the behaviors they like and punish the ones they don't.
The sort of "fairness" fairtaxers speak of is a level playing field where EVERYONE gets a bite at the apple without regard to what uncle sugar likes or doesn't like this week!