Ryan Murphy isn’t budging after the Menéndez brothers threw shade at their portrayal in his new Netflix series ... and while he's at it, he's also defending the incestuous storyline between the duo.
The director was scratching his head over why Erik and Lyle were so mad about "Monsters: The Lyle and Erik Menéndez Story," especially since he said he knew for a fact they hadn't even watched the show yet.
Addressing Erik's lengthy criticism in particular, Ryan told E! News at the "Grotesquerie" premiere he hoped Erik actually watched the series -- adding if he did, he'd be unbelievably proud of Cooper Koch, the actor playing him.
Ryan also pointed out the show was trying to unpack all the different theories of what happened before, during, and after Lyle and Erik shot their wealthy parents, José and Mary Louise "Kitty" Menéndez.
One of the theories addressed on the show is that the brothers were involved in an incestuous relationship -- which Ryan noted some people believed happened, while others don't think so.
Despite the brothers ending up with life sentences, Ryan said the show's all about letting the audience decide who the real monster is. Plus, he’s hoping to kickstart some important conversations about male sexual abuse.
As we reported ... Erik wasn't exactly on board with that view -- blasting Ryan for his "naive and inaccurate" portrayal of the brutal home slayings that made international headlines.