My objection to “dwarf planet” is purely a linguistically aesthetic one.

“Dwarf planet” ≠ planet

…implies…

“Dwarf person” ≠ person

…and I feel like the people under 4’10" (147 cm) would object to that distinction.

Also, “planetoid” was a perfectly cromulent word which Star Trek had been using for decades already.

Different meanings. “Dwarf person” = a person with dwarfism, but “dwarf planet” ≠ a planet with dwarfism.