It's the latest and dumbest chapter of the assumption of the figure of Columbus into the right-vs-left American culture war, in which the reactive American right has been compelled to champion and obsess over the historical and cultural validity of an Italian explorer born in 1451, who never even physically set foot on the land that would become the continental U.S.A., because the left dared to add context to the historical record.
If that line sounds familiar, it's because that's what Soprano told his son AJ after he criticized Columbus in a 2002 episode. Like it took guts to murder people and put them in chains, AJ scoffed about Columbus. He discovered America is what he did! a livid Tony replied. He was a brave Italian explorer, and in this house, Christopher Columbus is a hero! End of story.