phrase
The Red Pill
Choosing to see an uncomfortable truth instead of remaining in a pleasant illusion.
Origin
From The Matrix (1999). Morpheus offers Neo a choice: the blue pill returns him to a comfortable simulation; the red pill shows him reality. Neo takes the red one.
Modern usage
Originally a Plato's-Cave-style metaphor about ideology. Has been co-opted by various online subcultures to mean 'realizing the hidden truth' about everything from politics to gender. The original framing is bigger than any of those uses.