Jean Hampton distinguishes three kinds of hatred: simple hatred, moral hatred, and malicious-spiteful hatred (Nietzsche's ressentiment). Simply having an aversion to someone because of some non-morally objectionable quality (e.g., he is a bore) is unavoidable and raises no moral issues unless one acts on the feeling in immoral ways. (Trying to avoid a bore at a party is permissible; killing the bore – though very tempting – is not.) Moral hatred is aversion to a person (e.g., a Nazi) because of the immoral cause with which he is identified, and is coupled with a desire to triumph over him and his cause. There is no desire to hurt the person simpliciter but only a willingness to allow such hurt if unavoidable in the pursuit of victory over his immoral cause. Malicious or spiteful hatred, however, has as its very object the attempt to diminish and hurt another and thereby gain competitive advantage over him and his status; and it is this kind of hatred, argues Hampton, that is both irrational and immoral.

I am inclined to agree with almost everything Hampton says – as far as it goes.