“Red pill” is a matrix reference (take the blue pill and go back to your normal life or take the red pill and “see how deep the rabbit hole goes”) high jacked by sexist dudes who see “taking the red pill” as waking up to (perceived) social injustice against men. They show up in threads claiming women routinely lie about being assaulted and hide behind male victims (which exist and need to be heard) as they deny that women can be victims. They get mad when a woman is in Star Wars. They are the kind of people constantly saying “me too went gone too far” and end up pushing crap like Gamer Gate. They are also generally very right wing/overlap with “men’s rights activists.”