A Dallas Mavericks fan was booted from the team's home matchup against the Sacramento Kings on Monday ... 'cause apparently calling for the GM to be fired for trading away Luka Doncic is a big no-no.
It all went down at the American Airlines Center, where at least two Dallas supporters made their frustrations with Nico Harrison crystal clear.
They had two bright poster boards that read "Fire Nico" on them .