Is it obligatory to boycott an irreligious friend who casts doubt upon matters of faith, and with whom religious discussions devolve into endless quarrels?

A Muslim's love and hatred should be for the sake of Allah. Exaggerated love for individuals is not commendable, especially if the beloved is immoral or an infidel. A companion should be advised with wisdom, but if they persist in their immorality, it is best to abandon them, as the Prophet, peace and blessings be upon him, said: "Do not associate except with a believer, and let no one eat your food except a pious person."