Anger is always concerned with individuals,... whereas hatred is directed also against classes: we all hate any thief and any informer. Moreover, anger can be cured by time; but hatred cannot. The one aims at giving pain to its object, the other at doing him harm; the angry man wants his victim to feel; the hater does not mind whether they feel or not.

Rhetorica, by W. R. Roberts. De rhetorica ad Alexandrum, by E. S. Forster. De poetica, by I. Bywater. 1924 (ed. 1952)