Is it correct to argue, based on Musa (peace be upon him) throwing down the tablets while angry, that one who commits an act of disbelief in appearance is not declared a disbeliever until we know what is in his heart?

Question:
May Allah reward you, Honorable Shaykh. A professor says that some people claim that if someone commits an act of disbelief in appearance, such as throwing the mushaf or bowing to a person, we do not declare him a disbeliever until we know what is in his heart. They cite the story of Musa (peace be upon him) when he threw down the tablets while angry. Is this statement and its evidence correct?

Answer:
My brother, can you know what is in hearts? Who says this? Does anyone know what is in hearts except Allah (Glorified and Exalted is He)? We judge by the appearance, but what is in the hearts is left to Allah (Mighty and Majestic). If someone displays disbelief, we rule that he is a disbeliever, but what is in his heart, we leave it to Allah (Mighty and Majestic). This is different from discussing the matter and clarifying the truth for him if it is hidden from him or obscure to him. That is a separate issue; discussing it is one thing. But to say that we must know what is in his heart—no one from the people of knowledge says this. It is said by the pretenders to knowledge and the ignorant. The scholars say: discuss it. Perhaps he has a doubt, perhaps he is a follower of taqlid (following a scholar without knowing his evidence) who thinks it is right. Clarify it for him.
As for saying "no, until we know what is in his heart," if you know the unseen, you have become one who seeks to know the unseen. You have become a partner to Allah (Mighty and Majestic) in the knowledge of the unseen. Who says this? Yes.