it takes one to know one

English

(idiomatic) expressing the same underlying character-judgment themes as pot calling the kettle black or set a thief to catch a thief.
(colloquial, childish) A retort to a negative accusation, implying that the accuser shares the fault.
Bob: You're an idiot!

Tony: Takes one to know one!
- 1949, Nial Kent, The Divided Path, page 358:
  There's an unkind saying that it takes one to know one, and it's almost true.
- 1947, Poet Lore, page 280:
  Anyone who appreciates Shakespeare as this author unquestionably does is another Shakespeare — it takes one to know one!
- 1946, Gore Vidal, Williwaw, page 45:
  “I’ve got a bad egg,” said Bervick. “I guess this was a pre-war egg.” […]
  “It takes one to know one,” said the Chief, referring back to the eggs.
- 1980, Gerald Ford, “Problems Multiply”, in A Time to Heal‎, New York: Berkley Books, →ISBN, →OCLC, →OL, page 209:
  Brezhnev pretended a scowl. "Kissinger is such a scoundrel," he said.
  But Henry was ready for that. "It takes one to know one," he replied.
- For more quotations using this term, see Citations:it takes one to know one.

an insult which is true about both the sender and the receiver