If atheists would discuss things with theists in terms of "You believe in something for which there is no lab-tested empirical evidence of, therefore, your belief lacks scientific support ..." but they don't. Often the case is of "You're a poor deluded ignorant for believing in such a fabrication called [deity's name]". That's where the discussion derails. Many atheists (not all, sure) look down on believers, because they consider them intellectually challenged somehow and, having rationallity as their own criteria, judge the theists as little children with underdevelopted rational abilities who need to be saved from their delusions of God.
Eden