I often see and hear people using particular Bible verses, or corrupt Christian leaders, or bad examples of religious ethics in their personal lives, as the reason for widespread atheism, and it makes my head swim. That's nothing but overgeneralization and finger-pointing. Few people would reject equal rights because of the Black Panthers or a single instance of reverse discrimination, I think. You can't oppose an entire way of thinking just because it has been abused or misinterpreted by some.
Blaming one bad example of Christianity for every atheist's rejection of all religion is illogical at best and prejudical at worst. The only thing you can say with any degree of certainty is that they led you and/or certain people you know to reject religion. You or they used it as a justification for atheism, lacking the motivation to understand the Bible more deeply or the open-mindedness to not throw out the whole barrel because of a few bad apples. Martin Luther didn't become an atheist because he disagreed with his Catholic leaders; he became a reformer and thousands of Europeans followed him. Rather than reject their religion, they tried to replace it with the truth.
If you want to identify an actual cause of atheism, then try the Age of Enlightenment. Try anthropology and cultural relativism. Try separation of church and state. Try capitalism and laissez faire. Try the rise of democracy and its emphasis on personal freedom instead of personal responsibility. Try the Industrial Age metropolis and the known effects of high population density on community and altruism. Try good old-fashioned apathy and egocentricism. Heck, try any or all of these; they're all responsible in varying degrees.
Or pick any individual and talk to them long enough to find the one person, the one instance, that tipped their inner spiritual scale from positive to negative at a time when they were most receptive to it. Everybody has one. And it's almost never the same.