Is insistence on listening to a specific type of music, which the listener believes does not incite immorality or indecency, considered a major sin if one does not repent? And what is a convincing response to such a person?

Listening to music and musical instruments is forbidden in Islamic law. It is not permissible to argue for its permissibility on the grounds that it does not lead to profligacy and immorality, for the texts have absolutely prohibited it. Among these is the saying of the Prophet, peace and blessings be upon him: "There will be among my Ummah people who will legalize alcoholic drinks, unlawful sexual intercourse, silk, and musical instruments." Narrated by Al-Bukhari as a definitive statement. And "musical instruments are all instruments of amusement," as mentioned by Ibn Al-Qayyim. Ibn Hajar Al-Haytami considered listening to musical instruments among the major sins.