People use 'stale' bread to make bread pudding, so it can't be 'bad' for you. Mind you, I can't say that about anything else that goes into making it! That's all I can tell you I'm afraid.
Alexander Fleming discovered that a mold called Penicillium (the cells are pencil-shaped when you look at them under a microscope) produces chemicals which kills most of the bacteria nearby. (The mold is green when it grows in large amounts, and is often found on bread. This, however, does not mean that eating moldy bread will cure your ear ache -- or anything else