This paper analyzes fanaticism from the perspective of social philosophy and the phenomenology of emotions as a phenomenon of groups. Beginning with a broad definition of fanaticism which includes innocuous and hard-core forms, the thesis is developed that fanaticism’s diverse forms can be described in terms of their specific emotional dynamics. Fanaticism should not be identified with hatred. Instead, the paper argues that the principal emotions of aggression attending fanaticism are indignation and contempt, which may be intermingled with hatred. Moreover, the affective dynamics of fanaticism are shaped by effective positive emotions. A study of German so-called K-groups of the 1970s reveals pride and feelings of superiority as dominant emotions. These emotions turn destructive when feelings of superiority mutate into contempt. The paper offers an explanation of why hatred and contempt are often confounded and intermingled. Hatred often follows the feeling of being neglected or inferior and is typically confused with indignation or moral anger. Insofar as it is not met with recognition, indignation remains powerless. This powerlessness provides the basis for hatred. The mistaken view that hatred is the sole motivating emotion in fanaticism obscures the role of other aggressive emotions, some of which are just as dangerous as hatred itself.