I'd imagine atheists are no different than anyone else except they don't blame some religion or fictitious being for their actions.
That is precisely the point, Gilbert. A Christian or a Muslim who wants to beat his wife will find plenty of justification in Bible or Koran (one prominent Southern Baptist scholar has claimed that wife battering occurs as a result of wife not being submissive enough to her husband). His religion tells him that his wife is inferior to him, that she must obey him. It is only one easy step from that to justify violence against her (she didn’t obey him, she was impertinent etc.).
Now an Atheist may beat his wife (though as I said, I think the incidence is probably much lower than among religious folk). However, where is he going to find justification for his action? He already thinks that Bible or Koran are nonsense books. So who is going to tell him that what he is doing is the right thing to do, that the highest power in the universe supports him?
A religious man has plenty of support structure which will enforce his views of women, an Atheist doesn’t have any. On this basis alone I would think that an Atheist would be less prone to violence against women.