Al-Khatib al-Baghdadi mentioned that the reason the Prophet (peace and blessings be upon him) prohibited them from saying "You are our master" was that they assumed lordship was a consequence of prophethood.

Question:
Honorable Shaykh, may Allah grant you success. He says: Between the words of Imam al-Khatib (may Allah have mercy on him), the reason the Prophet (peace and blessings be upon him) prohibited them from saying to him "You are our master," even though he (peace and blessings be upon him) is the master of the children of Adam, is that they were recent converts to Islam, and they assumed that lordship was a consequence of prophethood.

Answer:
This includes this type and others; it is a general statement. The important thing is that one should not confront a person with praise. One should not say, "You are the master, you are noble, you did this, and you did that." This is not permissible. If you see the flatterers, throw dust in their faces; this is in the hadith.