"Doctor Glas" by Hjalmar Söderberg (1905)

Typically, people are messengers for evil ideas, instead of being evil themselves. In such cases, one should focus one's efforts on fighting the attraction of these ideas, instead of eradicating the messengers. This is also why a murder is unlikely to be a satisfying experience. After the act, the murderer discovers that these were the ideas that he found repugnant, not the carrier of those ideas; those ideas survive, if only in the mind of the murderer.