Believer says: Just because you don’t believe Christian doctrine doesn’t mean it isn’t true.
But skeptic says: But not believing it is largely beside the point. We look for validation.
Look at it the other way: Just because you assert a doctrine, it doesn’t mean it's true. It’s really a matter of finding out whether the claims are true. A Christian may want to claim authority in the Bible, but he needs to explain why his source is true. I don't mean merely say, "Because it’s the Bible."
Recap: Just because you don't believe the atheist perspective doesn't mean it isn't true.