What this tweet — and the thread that follows (not very original, of course; this has been in the public discourse for years) — reminds me of is that popular history is a set of myths. It shouldn't really matter whether Columbus was a deluded and cruel nincompoop or a seafaring genius; it shouldn't really matter whether he even existed. His real historical character is no more important than that of Aeneas. And of course those who celebrate Columbus day while sharing the national myth, are unlikely to celebrate him for being "a bumbling slave trader who was bad at math".
Christmas is a good example of knowing perfectly well that something isn't historically accurate — that there isn't a Santa, or that Jesus may have never been born — but at the same time completely ignoring the historical knowledge and just happily going along with the myth.
But for myth-busters and iconoclasts, it's somehow important to set this particular myth straight.
On the other hand, Russia has also gone through a change of its foundational myths and holidays in the recent past, and there also were people who thought it important.