What is the ruling regarding one who says that there is entertainment in Islam and that the Prophet of Allah, David (peace be upon him), was an entertainer?

Islam permits recreation through permissible means, provided there is moderation and no neglect of an obligation or commission of a prohibited act. The statement that David (peace be upon him) was a "singer" (مطرب) is an ugly and reprehensible assertion, and its utterer deserves disciplinary action. The word "مطرب" (singer/entertainer) is used for people of immorality and revelry, and to describe a prophet with it, whether in contempt or dispraise, is an act of disbelief. The characteristic of a "singer" (مطرب) is not befitting the stature of prophets. Allah bestowed great favor upon David (peace be upon him), for he would recite the Psalms with a voice unlike any ever heard, and humans, jinn, birds, and animals would gather to listen to his voice.