Anything-centrism is "bad" in that it clouds one's ability to be objective. It also impedes empathy.

It's sort of tied to identity. If you do not cling to a specific identity, then it frees you to empathize with a wide range of people. If you say "I am white/asian/tall/rich", then it forms an in-group vs out-group mentality, and obstructs empathy.

For example, does it strike you odd that any land should be deemed "discovered" when there are already inhabiting humans there?

I'm normally pretty skeptical of anti-european sentiments, but in this case I'd be fine with changing the name of the holiday.

Whatever your viewpoint, the exploration of America was pretty complicated and complex, and even just the story of discovery alone is more than Columbus. So open it up, celebrate all the explorers involved. If you've got a story to tell about the first people across the land bridge and down into the continent, let's add that too.

I'd be fine with celebrating the entire story of the exploration of the continent.

Anything-centrism is a cognitive bias, it reduces complex issues to simple ones designed to suit your world view. It's a pretty nasty ignorance promoting concept.