I hear that an evil person should not be hated.

Answer

The concept of hating/ loving a person for deeds, could be understood on the basis of a father's reaction to his son's evil. If the son does evil, the pious father will scold and even hit the son, but he goes on loving the son. He does not hate his son. Similarly, when a Muslim commits an evil, we hate the evil, and while we naturally have no love for him, we should not despise him, for it is quite possible that he will reform, and it is quite possible that the one who despises another may become evil. It has happened to innumerable people. The misdeeds must be hated.

The dividing line is fine and even blurred, and sometimes to hate the person is valid. For example, it is not expected of a person to love someone who insults Rasulullah (sallallahu alayhi wasallam), or who mocks at any Sunnat act. A man will naturally not love and cannot love someone who robbed and murdered his father/son, or who violated the honour of his wife/daughter.

Rasulullah (sallallahu alayhi wasallam) said: "Hatred is for Allah's Sake, and Love is for Allah's Sake." Hating only the deed, not the person is not an all-embracing principle.