The answer to this question is based on understanding how Loshon Harah comes about. The Chofetz Chaim points out that one of the prohibitions that a person violates by speaking Loshon Harah is Chillul HASHEM. He explains that if someone has a powerful desire to commit a sin and then transgresses it, it may be a serious offence, but there is a mitigating factor – he fought a battle and lost. Loshon Harah, on the other hand, is very different. There is no driving, instinctive force that pulls us to speak disparagingly about other Jews. There is no magnetic pull that tugs at us. Therefore, if a person speaks Loshon Harah, it can be a Chillul HASHEM; since he is committing this sin without any powerful desire, it must be that he utterly disregards the command of the King.
