Hate is a negative emotion, however it is a necessary emotion. Balancing positive and negative emotions in your life is the key to mental health. Hate allows human beings to focus their energy into defeating their enemies without guilt and without remorse. This is necessary. You have to balance this with love of the innocent and love of your family and friends. Don't be afraid to hate those that victimize the innocent, don't be afraid to act and defend the weak from evil. To quote a very wise phrase, "the only thing necessary for evil to triumph is for good men to do nothing." I know this quote was originally attributed to Edmund Burke, or possibly Mills, either way the concept is sound and true. (Quibbling over provenance is a waste of time and energy.)