Can Theists Be Moral?

That’s a pretty silly question, isn’t it? I would argue that it is about as silly as the question, “Can Atheists Be Moral?” Even fundamentalist Christian philosophers grant that atheists can know moral principles and behave according to those principles. If someone wishes to deny that theists or atheists can have morals, it seems the burden of proof should fall on them to offer some reason why they could not have morals.