Joker, no matter which incarnation/universe, NEVER likes to be used as someone's unwitting pawn. So it makes sense he takes GREAT offense to not being made privy to the truth about the Injustice League.
It's interesting that Joker is not affiliated with Klarion; the Witch Boy is a Lord of Chaos and Joker claims to be an Agent of Chaos in most versions.
It's possible that only magical beings can be a Lord's agent.
Number 16: Tigress, Cassandra and Onyx infiltrate Section 16 of Santa Prisca.