Why would anyone ever get upset about someone telling other people they were servants of God who were telling people the way to be saved? Sounds like a compliment to me. But that is exactly what happened with Paul the apostle in Macedonia. A slave girl who had a spirit of divination followed them around saying ”These men are servants of the Most high God who are telling you the way to be saved.” Paul put up with it for a few days but finally turned to the girl and commanded the demon come out of her. At once the demon left her and she no longer could practice the evil craft that brought her masters much money.
Why did Paul respond this way? What she was saying was  true. After all isn’t any witness a good witness? No. While what she was saying may have been true Paul would not want the message of the Gospel associated with an evil spirit. Dong so legitimizes the demonic spirit in the eyes of those who witness the event and clouds the very clear line between the true power of God and the counterfeit power of Satan. Even though what she was saying was true it came from a false witness. Beware the false witnesses, wolves in sheep clothing, even when a part of what they say may be true.