The sign, which hung over the 37-foot tall Green Monster, read, “Racism is as American as baseball,” with white lettering over a black background.
The sign was hung only for one batter during the fourth inning. The umpires asked for the sign to be removed because it was in fair territory. There was a chant of boos from the crowd when Red Sox security was forced to remove the sign and escort the protesters out of the ballpark.
According to a Red Sox spokesperson, four fans were removed from the park, and one of those fans said they were inspired by the Black Lives Matter movement.
The Boston Antifa, a left-wing activist group, took responsibility for the protest and explained why via Twitter.
The Red Sox lost to the Athletics, 7-3.
This was not the first time the Red Sox had confronted racism at Fenway Park this season. In May, Baltimore Orioles outfielder Adam Jones said fans yelled racial slurs and threw peanuts at him during a game.
Jones received an apology from the Red Sox organization the following day and a standing ovation from the crowd when he stepped up to bat.
A night later, the Red Sox permanently banned a fan from the ballpark whom they said used a racial slur toward another fan.