It Really Comes Down to Astronomical Arrogance

So Dr. Tyson admitted that the decision to declassify Pluto was more of a bit of Earth-based arrogance than anything else.

The downgrading of Pluto came after the discovery of Sedna in 2003 made it evident that there could be even more planets further out. Astronomers, who faced the possibility of having more planets than they had fingers to count them, had to do something about that. So they reclassified Pluto. And so Pluto was demoted.