I've heard this said a few times during my visits to Creationist Facebook pages and it never ceases to make me wonder how insane their argument is if you actually give it some thought.
First we must establish what atheist means:
Someone who denies the existence of god
Let us, for argument’s sake, suppose the Abrahamic God of the Old Testament exists. He’s sat up there, reminiscing on all of the things he has done in his life. This would include mass genocide perpetrated against those who don’t believe in him and the murder of babies. Yahweh, for that is supposedly his name, is not a forgiving God, far from it. He is depicted as a tyrannical dictator with a fine line in demanding wholesale slaughter.