In the past, I've cut the mold off of cheese, but the rest of the cheese still tasted nasty-moldy, and I ended up tossing it out anyway.
Bread, likewise. In sealed plastic bags as it is now packaged, the entire loaf, or what remains of it, is tainted.
It seems, according to some research I've done, that mold has microscopic 'roots,' 'threads,' or 'runners' that go into the food far past what is visible to the naked eye.
That explains my prior experiences, and the research also states that some, but not all, contain assorted toxins, the worst of which are carcinogenic.
Since there are about a bazillion types of mold, and unless you are a biochemist equipped with a microscope, and can identify the particular strain that has affected your food, it's a 'better safe than sorry' scenario. Or, as my mother used to say, "When in doubt, throw it out."