1. It takes a greater leap of faith to be an atheist than to believe in God. It takes a greater leap of faith to be an atheist than to believe that, at Mass, a little white piece of unleavened bread becomes God in the hands of a sinful priest. What you're saying, if you're an atheist, is that in the beginning, there was Nothing. Nothing turned its non-existent self into Something. Something magically evolved into stars, planets, galaxies, dinosaurs and men. By pure chance, these things all continue in being and do not wink out of existence. Also by pure chance, they are governed by the laws of physics. You believe all this nut stuff, explicitly or implicitly, but you, who claim to be a disciple of Science and Reason, think I'm the loon.
2. There is no such thing as a principled atheist. St. Paul blasts that notion out of the water in the first chapter of his Letter to the Romans. Some people disbelieve in God because that's what they were taught. These have not arrived at atheism by an exercise of reason, but are merely taking what they have been given. They have a duty to investigate the truth of what they have been taught. Some people reject the existence of God because of some trauma they have suffered. These have not arrived at atheism by an exercise of reason, but based on emotion. They need prayers. Some people choose to disbelieve in God because they are attached to some vice they don't want to give up. These have not arrived at atheism by an exercise of reason, but because they are enslaved to their passions. They know that to acknowledge the existence of a Creator means acknowledging their duties toward Him, and His claims on them. This would get in the way of doing whatever they want. I suspect these are the majority.
3. Atheists like to argue that religion is evil because of all the people who have allegedly been killed in the name of religion. This argument is generally trotted out without specifying a religion, and without distinguishing between aggressors and defenders. It is easily disposed of. The number of people killed in the name of religion is dwarfed by the number of people murdered in the name of atheism since the French Revolution. It was the great atheistic republics of the last two and a half centuries that gave us murder and destruction on an industrial scale. Over the course of three and a half centuries, the Spanish Inquisition may have turned between 3,000 and 5,000 people over to the secular arm to be executed. This figure is dwarfed by the millions upon hundreds of millions slain by the governments of revolutionary France, the Soviet Union, Red China, Nazi Germany, North Korea, Cambodia -- every one materialist, totalitarian and officially atheistic.
4. Which brings us to the inescapable conclusion that atheists are far more insistent on shoving atheism down everyone else's throats than believers -- at any rate, Christian believers -- are at pushing their creeds. Islam has always been notorious for sword-point conversions. Atheism, which has enlisted swords, guns, bombs, spies, snitches, prisons and insane asylums in its wars against throne and altar, can hardly claim to be gentler.
5. In the words of Bing Crosby's Father O'Malley in Going My Way: you even throw like atheists.