Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) said:
Undoubtedly the Muslim is obliged to hate the enemies of Allaah and disavow himself of them, because this is the way of the Messengers and their followers. Allaah says (interpretation of the meaning):
“Indeed there has been an excellent example for you in Ibraaheem (Abraham) and those with him, when they said to their people: ‘Verily, we are free from you and whatever you worship besides Allaah, we have rejected you, and there has started between us and you, hostility and hatred for ever until you believe in Allaah Alone”
“You (O Muhammad) will not find any people who believe in Allaah and the Last Day, making friendship with those who oppose Allaah and His Messenger (Muhammad), even though they were their fathers or their sons or their brothers or their kindred (people). For such He has written Faith in their hearts, and strengthened them with Rooh (proofs, light and true guidance) from Himself”
Based on this, it is nor permissible for a Muslim to feel any love in his heart towards the enemies of Allaah, who are also in fact his enemies. Allaah says (interpretation of the meaning):
“O you who believe! Take not My enemies and your enemies (i.e. disbelievers and polytheists) as friends, showing affection towards them, while they have disbelieved in what has come to you of the truth”
But if a Muslim treats them kindly hoping that they may become Muslims, there is nothing wrong with that, because this comes under the heading of softening their hearts towards Islam. But if he loses hope of them becoming Muslim, he should treat them in the manner that they deserve. This is explained in detail in the books of the scholars, especially Ahkaam Ahl al-Dhimmah by Ibn al-Qayyim (may Allaah have mercy on him).