Why does he say "beast" here?
Native speaker’s answer
Rebecca
"Beast" is usually used to refer to an animal, or perhaps something or someone that is either cruel, unsavory, or unpleasant. The speaker precedes "beast" with "gentle" as it has special functions for washing delicate dishes, so perhaps he is viewing the dishwasher as a type of strange creature that is surprisingly gentle. It is meant to be a humorous quip. Ex: He's a beast. He stole his company's money and ran away. Ex: The murderer was vilified as a beast by the media.