Dallas Mavericks fans clearly still loathe Nico Harrison for trading away Luka Doncic ... one actually yelled right in the GM's face on Monday, "Fire Nico!" -- repeatedly!
The scene unfolded just before the Mavs' tilt with the Brooklyn Nets at American Airlines Center in Dallas ... as Harrison -- who jettisoned Doncic to the Lakers back on Feb. 1 -- was saying hi to some people who had shown up for the game a bit early.