And mixins, by all accounts having their origin in an icecream store, and being as they are inherently an introduced novelty, are an indication of the extent to which the theorists are willing to embrace the farcical for the sake of conformance with the aforementioned meme of purity.
That's not really fair. The name has its origin in an ice cream store (as did other puns in the Flavors language, like having 'vanilla' as the name of the base class), but I don't think anybody can seriously say that this is any sort of real-world metaphor for the language.
Mixins are just one way of decomposing a system. Sometimes appropriate and sometimes not.