Like everything else worthwhile in life, to "Love your fellow as yourself", the great principle of the Torah, is a real challenge. The human personality is not only prone to irrational hatred, it tends to find it enjoyable, or at least distracting.
The discourse Heichaltzu (lit. "arm yourselves") by the fifth Lubavitcher Rebbe deals with the spiritual roots of such hatred, its practical consequences, and how one can experience and express true love. As in all Chasidic thought, the emphasis is not so much on how bad is bad, but the spiritual pleasure and feeling of true worth that one is missing when he succumbs to evil.
Includes several related essays and letters as well as extensive footnotes and references.