What is the ruling on dealing with a person who insults the religion, and does sin fall upon whoever exchanges kind treatment with him or sits with him?

The phrase "cursing religion" is an act of disbelief that expels one from the fold of Islam. However, some scholars have differentiated between cursing the religion of Islam and cursing the religion of a Muslim. Cursing the religion of Islam is an act of disbelief. As for cursing the religion of a Muslim (such as saying "may your religion be cursed"), it may not be an absolute act of disbelief if the intention is to condemn his bad manners or his actions that violate religion, and not the religion itself. Accordingly, the one who utters such phrases does not commit an act of disbelief if he does not intend to curse the religion of Islam. However, it is a reprehensible act that must be denounced, and he should be advised and warned about the seriousness of his action and the necessity of repentance. If you are unable to advise him, do not sit with him in any gathering where such words are uttered. It is permissible to pray for him, wish him well, and smile at his words that do not offend religion.