Feuerbach is saying: No, wait a minute - if you are going to be allowed to go on living as you are living, then you also have to admit that you are not Christians. Feuerbach has understood the requirements but cannot force himself to submit to them - ergo, he prefers to renounce being a Christian. And now, no matter how great a responsibility he must bear, he takes a position that is not unsound, that is, it is wrong of established Christendom to say that Feuerbach is attacking Christianity; it is not true, he is attacking the Christians by demonstrating that their lives do not correspond to the teachings of Christianity.