Well, they also once vetoed Pluto itself - that 2% of astronomers got rid of a whole planet is the only reason anyone has ever heard of the IAU. Their own arbitrary rules instead say Kerberos and Styx, which placed second and third, win out. What rules?
They say moons must be named after characters from the underworld of Greek or Roman mythology - and Vulcan is - but then they say Vulcan is not 'associated' with Pluto. How unscientific! If volcanoes don't originate underground, where do they came from, Uranus? It's rather suspect reasoning, and they know it, so they trotted out another reason even more suspect: Vulcan was the name given to a hypothetical planet that never even existed and therefore is 'already in use'.(1)
Credit and link: SETI
Yes, a hypothetical planet created to account for the odd movement of gravity is the reason Spock's homeworld can't get honored. Shatner was indignant on his Twitter feed:
"So they name a moon Kerebus because there's already a Cerebus asteroid but a mythological planet knocks out Vulcan?" and "Star Trek fans have had it rough. First JJ (Abrams) blows up Vulcan and now SETI finds a loophole to deny it from coming back!"
Well, maybe they will toss Shatner a bone and name a crater after Kirk or something.
Mr. Shatner, stand up if you don't like it. The IAU only has authority if you let them have authority, they gave themselves this power and fight off anyone who points that out - why even consider a poll for names if you have already decided what names are not going to win?
It makes me want to reconsider my stance on Uwingu's Baby Book of Galactic Names.
(1) The new Star Trek movie used Nibiru, another mythological planet, which I thought was clever.