If someone prophesies in the name of the Lord and the prophecy doesn't happen, that prophet is a false one. Period.
So mere human beings who happen to have prophetic gifts are infallible? That is what this statement implies.
Do you really imagine that God is so stupid, insignificant or powerless that He cannot arrange to vindicate His own Word and see to it that the false prophets or charltons eat dirt?
When a crowd of children, likely educated by their parents' opinions ran after Elijah taunting him with, "Go up, you bald head.." God confirmed Elijah's status very readily. Read the story at 2 Kings 2:23.
To the children and their parents Elijah wasn't much but God isn't happy with even little children mocking the least of His servants. Take a hint.
Don't like him? Too bad. Don't approve, ask the man's Master to bring correction but for the sake of your own well being have the sense to honor God's word which is what brought us morality and integrity in the first place.