Mete mierda es algo fuerte, ¿no te parece?
Considerando que las dos explicaciones que da el Urban Dictionary son:
1. to talk trash about a friend or aquaintance, to publicly denounce or disrespect. When throwing shade it's immediately obvious to on-lookers that the thrower, and not the throwee, is the bitcy, uncool one "How does Kimmy keep any friends? Last night at the party all she did was throw shade at people."
2. To hate on someone for acting a fool. That bitch was TRIPPING last night . . . THROW SHADE