It might be considered by some politically imprudent to hate Columbus, though one might also wonder why simply being Italian should make one consider a racist, enslaving Spanish colonist a hero simply because of where he was born. But be that as it may, let's also remember that although it's true that New York has the highest percentage of Italian-Americans around, it's still only a bit under 9 percent, a much smaller percentage than that of Blacks and Hispanics, and not so evenly distributed either. Now one can also have varying opinions about political opportunism and so forth, but it is at least imaginable that Mamdani may have figured out the relative likelihood of different ethnic groups to vote for Cuomo anyway, and worrying less about them than about those who might provide support.
In any case, it seems possible that Hercules56 has not entirely disentangled the question of whether his objection to Mamdani's statements is because he considers them impolitic or because he considers them wrong - though of course it could be both.