Gilbert Arenas -- Calls Rev. Al Sharpton a 'Coon' ... Over Michael Brown Protests

Gilbert Arenas uncorked a racial slur on Rev. Al Sharpton ... attacking him over his reaction to the police shooting of Michael Brown and the riots that have followed.

Arenas posted his rant on Instagram, saying ... "the stats also show AL coon sharpton has not helped one situation he has protested at,he actually made it worst and because of him the jury goes the other way."

Gilbert's post included a plea to Michael Brown's family to leave Sharpton out of planned protests. He said, "FAMILiES of the victims pleaseeeeee stop asking #alsharpton to speak or ur behalf,you have a better chance having #caesar the monkey from #planetoftheapes to get justice for you."

Gilbert appeared to be reacting to news coverage of Sharpton arriving in the St. Louis area and marching arm-in-arm with protesters.

As if the racial slur wasn't enough, Arenas added, "#AL ur like a #THOT in the club,lookn for attention what u said at trayvons rally #enoughisenough ur right were tired of u PRETENDING."

If you don't know ... THOT is another term for ho. It appears Arenas took down the original attack, but he rips Sharpton for not showing up in St. Louis until the national media showed up there too.