To realize/tell somebody how stereotypical you/they are.
Originates from the first verse of the song "admit it"-say anything, which has lyrics that make fun of every stereotype you could think of.

LYRICS:
Admit it!
Despite your pseudo-bohemian appearance

And vaguely leftist doctrine of beliefs

You know nothing about art or sex

That you couldn’t read in any trendy New York underground fashion magazine

Prototypical non-conformist

You are a vacuous soldier of the thrift store Gestapo

You adhere to a set of standards and tastes

That appear to be determined by an unseen panel of hipster judges (bullshit)

Giving a thumbs up or thumbs down to incoming and outgoing trends and styles of music and art
Go analog baby, you’re so post-modern

You’re diving face forward into a antiquated past
It’s disgusting, it's offensive, don’t stick your nose up at me.