Justin Bieber -- Free Breezy!

Justin Bieber went tagging in Colombia last night with a clear message -- GIVE CHRIS BROWN A BREAK!!!

Biebs got all Banksy in Bogota where street art is permitted... spray painting "Free Breezy" on the side of a wall.

J.B. also tagged a pro-pot message on the wall ... and paid tribute to his dead hamster Pac.

So Bieber, along with a Secret Service agent ... are doing C.B.'s bidding.