We really just didn't realize the diversity of planetary types in our solar system. Pluto looked like a misfit because it was the only one we saw. And just as a Chihuahua is still a dog, these ice dwarfs are still planetary bodies. They're large enough to make themselves round by self gravity, and they surely pass the test of planethood.

Just because Pluto orbits with many other dwarf planets doesn't change what it is, just as whether an object is a mountain or not doesn't depend on whether it's in a group or in isolation.

When we first sent missions to Jupiter, no one expected to find moons that would have active volcanoes. And I could go down a long list of how often I've been surprised by the richness of nature.

Alan Stern Quotes