Okay, but for example, the man then says in the same statement that the Bible might be wrong sometimes. Of course, if he were to remember that the Christian doctrine says that it is the Word of God, then he won't say such a thing. But immediately, he remembers that the Bible is the Word of God Himself. (Or, he may be reminded by the other Christian). And, he also had accepted the doctrine at first - he just had forgotten it during their argument, and so corrects his statement and apologizes. Does that mean he just committed heresy and he had become a heretic?
The bible is not the word of GOD himself. It is a witness of men of the word of GOD. The bible is a book; the word of GOD is a living being.