Whatever white activists might say, the case against Columbus Day isn't aimed at the particular actions of Cristoforo Colombo. The case against Columbus Day is aimed at the fact that he's an unambiguous symbol of the conquest of the indigenous peoples of the Americas, many of whom are American citizens, who deserve a modicum of respect. Again, America is a "multi-nation" state, which is composed of non-indigenous people and various indigenous peoples. This holiday effectively celebrates the forcibly conquest of the later, which is pretty repulsive. Columbus Day simply can't be reconciled with American commitments to the Nez Pearce or the Shoshone or the Crow etc.
Columbus Day controversies may be symbolic but sometimes symbols matter and the attachment to this particular symbol represents the insidious ways that many Americans view the original cultures of this continent, who are either romanticized or treated as barbarians in need of civilizations. They're still alive.
Is Thanksgiving a problem then?