The difference between debating the so-called "FairTax" and the repeal of the Sixteenth Amendment is that the latter is not the least bit politically realistic. A Congressman who proposes such an idea IMHO is not going to be taken seriesly when proposals that have a chance are taken up. Or perhaps his introduction of the Bill is a gesture designed to throw a red meat appetizer to people. That's fine, but let's not kid ourselves about just how unrealistic a straight repeal of the Sixteenth really is. 2/3 of each House? C'mon.
I agree that the King Bill by itslef is DOA as you say. However, if the FairTax is able to be passed, the 16th amendment would be moot. I don't think that King is profering with any crazy notions that it will be passed on it's own merit. I think it is meant to compliment the FairTax Bill, which calls for the 16th's repeal, but does not have the authority to do it itself.