PZ beats the dead horse of the Christian myth of amoral atheists some more.
What really gets me about this claim, isn't the obvious implicit statement "you are amoral" -- rather it's the suggestion that the Bible or simply a "belief in God" makes one magically moral. How the hell does that work? You need to ignore massive chunks of the Bible to even make it coherent, and damn near all of it to make a moral system out of it. Pretty much the only thing you are left with is the Golden Rule and that's been produced hundreds of times (in fact Matthew 7:12 where it appears attributes it as "for this is the law and the prophets" rather than Jesus saying he made it up himself). Also, it's more moral in the negative creation than the positive creation. Do not do unto others as you do not wish them to do unto you. If you don't want to be killed, don't kill. However, in the positive formation it would be fine for the mafia to murder a snitch, because they would expect the same.
How does belief in God make a person moral? What magical criteria does one use to sort the nasty bits out of that book? Implicit, almost always, in the claim that atheists are amoral is the claim that religion makes religionists moral or theism makes theists moral. That's the bigger lie.
I dare say it is slightly incumbent on me to explain why I'm moral, or which moral theories I tend to prefer (though it's nearly impossible to come to that conclusion without some major problems in your thinking). However, the assumption that they are moral because of religion or God belief, can't be established. The better response is to turn the question around and ask them where they get their morals and when they say "the Bible", backup slowly, apologizing, and pleading to not be stoned to death.
As if people don't natively understand the very basics of morality. A lot of human instinct has been tuned to this purpose. Empathy, love, reciprocity, pain, anger, sense of fairness, mercy, and other deeply ingrained bits of ourselves goes into keeping us moral, worked out over millions of years by tinkering and they want to give credit to their book. Moral systems take a lot of time and energy to evolve and they want to say that it magically flows from their book! A central focus of which is small amounts of moral understanding between ingroup members and no respect for outgroup members. This isn't the source of morality, these are moral understandings best left to die in order to give rise to better and improved morality within changing zeitgeist of moral philosophy. However religions want to give them a pedestal. It is a testament to human morality that so many religious individuals are moral in spite of the Bible.