Justin Bieber isn't taking too kindly to being told he doesn't deserve a Grammy -- going after the Black Keys drummer who insulted him ... saying, the drummer "should be slapped around."
Bieber added "haha" at the end of his statement -- which he posted on Twitter -- like he was joking.
the black keys drummer should be slapped around haha— Justin Bieber (@justinbieber) February 12, 2013
TMZ broke the story ... BK drummer Patrick Carney mocked Bieber's Grammy snub after the awards on Sunday -- telling TMZ, "He's rich, right? ... Grammys are for music, not for money ... and he's making a lot of money."
Grammy count -- Black Keys 7 ... Bieber 0