This objection is an illogical objection. The Bible tells us that God cannot lie and it also tells us that he can do all things he desires to do. Obviously, God can only do that which is consistent with his nature. He cannot stop being God. He cannot stop being holy. Omnipotence does not mean God can violate his own nature -- like stop being omnipotent and then become a blue berry. A blueberry is not by nature God; therefore, God could not be a blueberry. But this doesn't mean he can't do all things he desires to do which is what the biblical definition of omnipotence means.