Your premise is faulty since, on average, atheists know more about Christianity than Christians do, as Pew reported (link below). Where’s the evidence that atheists dismiss Christianity without ever considering what Christians have to say?
But you’re saying that atheists’ tendency to dismiss or at least to reject Christianity is itself evidence that we need Christianity to be true, because that rejection shows we’re not saintly beings. We dismiss Christianity because we’d rather go on sinning.
That argument commits the ad hominem fallacy. You’re saying the existence of atheism shows that atheists are bad people, like everyone else. Yet that question has no bearing on whether atheism or Christianity is true. It’s a red herring. What you’re trying to do here is to apply something like Pascal’s wager, to attempt to steer atheists into pondering how things would be if Christianity were true, to train them to contemplate that scenario until they’ve gotten used to the idea, thereby bypassing logic and science, and joining your club.
Of course, humanity isn’t saintly, but that’s evidence that we evolved by natural selection, and that the Christian contention that we were created by a perfect deity is dubious. Christian theology says our lack of saintliness amounts to an original sin, like the Jew’s alleged sin of being Jewish, according to Nazis. The grotesqueness of that anti-human Christian theology, too, is evidence of our lack of saintliness, and of that theology’s all-too human origin.
Your last paragraph begs the question when you say that atheists mean to out-think God. No, it’s human theists whom atheists mean to out-think. You’re just presupposing that God exists, which is the very question at issue.
