Again: When an atheist and a Christian sit down at a table, you have exactly the same thing on either side of the table: an intellectual with a big ego and a certainty that he’s right. Neither side has the ability to prove themselves superior *before* meeting in the marketplace of ideas. Obviously neither side can prove that it is superior; they're all fallible human beings. It's only the marketplace of ideas that will eventually distinguish between the two.
Quit trying to exclude one of the parties before the contest even begins. Or, if you have to exclude someone because they've fallen short of expectations, then exclude the Christians; they're the ones that claim to have infallibility on their side. Christians are the ones falling short of their own high expectations. Athesists, on the other hand, never claimed to be anything more than fallible.