There seems to be a very wide consensus, in my experience, that Atheists don't know The Bible. This is categorically false. While it may be true that not ALL Atheists know scripture, the idea that being an Atheist, or simply not believing in the presence of a supernatural deity who oversees everything that every person on Earth does throughout their entire life, automatically means that Atheists don't know scripture is a gross over-generalization, and one that does little more than breed contempt for one of the largest minority groups in the U.S.
The fact is that Atheists, in a very large part, do know The Bible. We are very familiar with scripture. In reality (and with no small amount of irony), it's the study of The Bible and its scripture that has led many of us to Atheism. There are a couple of pervasive points Christians tend to bring up to support their claims that Atheists don't know The Bible.
One such claim is that without guidance from "the good book," Atheists don't know (or can't define) morality. Again, this is false. many Atheists have come to understand that morality is a matter of survival of the species. Is it really valid to say Atheists don't know any moral code simply based on the fact that we don't believe in the teachings of The Bible? I should think not. We are well aware that killing people, and stealing their things is directly counterproductive to harmony, and anything that is counterproductive to harmony is also a hindrance to survival. In other words, doing what is morally the right thing to do is not a matter of faith, it's a matter of survival. It's a primordial response to living as social animals. Killing people drastically decreases the number of people available to mate with, and would therefor hinder our species' ability to reproduce.
Another claim is that Atheists are simply angry at God, or rebelling against their upbringing, While in some cases this may be true, these are not true Atheists. Atheists, by definition, don't believe in God. Without believing in God, how can we be angry at him? As to the second part, rebelling against their upbringing; how can Christians assert that Atheists don't know scripture and simultaneously claim that they're rebelling against their upbringing? Wouldn't that claim imply that the upbringing against which they are supposedly rebelling was chock full of scripture and indoctrination?
In all honesty, a majority of Atheists DO know scripture. The problem we have... indeed, the very reason we are Atheists... is that scripture is rife with contradictions. I can only speak for myself, but one thing I've noticed that is directly correlated with the contradictions in The Bible is the contradictions of the people who follow it. For instance, Matthew 7:1 says "judge not, lest ye be judged," yet many Christians point angry fingers at Atheists and tell us we're going to burn in hell. We're going to burn in hell because we don't believe in an all-loving deity who will throw us into a fiery septic tank if we don't love him. Isn't that a judgement? Aren't you explicitly forbidden to do that?
Through my experience, and all my debates with many Theists, I have seen one trend that glows like the straw man they burn: The more an Atheist knows about scripture, the angrier the Christian with whom he's debating gets.