I honestly wouldn't have had a problem with it being grandfathered in. I love Pluto too. I'm just saying that from a strictly scientific standpoint they got it right.
Also for all the credit Neil deGrasse Tyson gets for Pluto's demotion he's more of a supporter of the idea than the root cause. He's among the most famous astrophysicists so his views on the issue are among the most well-heard but he's really only driving the getaway car. If you want a better culprit go with Mike Brown of the IAU, who wrote a 2010 memoir called "How I Killed Pluto and Why It Had It Coming." He's the one who is actually taking credit for it. Tyson is only justifying it.
A bit late to reply, but I would have said what Chief did - it should have been grandfathered in. Sedna and ilk clearly demonstrate Pluto isn't alone, and likely one of countless others. But there are three factors. First, Pluto is still special. It's discovery by Clyde Tombaugh (sp) was rather unique and amazing. No other KBO comes anywhere close to actually becoming the 8th 'planet', meaning, Pluto is unique in it's proximity to the sun. I strongly disagree with the IAU's assertion that Pluto hasn't 'cleared out it's neighborhood' because Charon's size is so close to Pluto. Charon is only 11% of the mass of Pluto - hardly a clear cut case for a binary system imo.
The KBOs probably are littering the outer reaches of the system, close by to one another, with strays close in size to the parent body common, and a vast majority of them not massive enough to have enough gravity to become somewhat round. Pluto... well, like I said with the 8th planet comment, Pluto is different, and applying any of the previous specifications to it is a stretch. Considering the historicity of Pluto, to demote it when it isn't cut and dry like other KBO's is just plain wrong.
There's the historical and cultural factor where generations learned of planet number nine.
But my main point of contention, and one which focuses more on Tyson, was the way it was done. I believe I said the decision harmed the reputation of astronomy greatly. It did so for the reasons mentioned above, the comical 'planet no longer a planet' situation. But more than anything - the IAU waited until the absolute end of the conference. What was it, like 90% of the voting body had left at that point (too lazy to look it up.) Bottom line, only a fraction of a fraction voted to demote Pluto. There was hardly a legitimate debate about it involving all the people who should have been involved. It was absurd and underhanded.
More than anything though, because of how they did it caused an extreme conflict amongst astronomers. When the news got wind, you had these details emerge along with astronomers infighting and commenting on how ridiculous the whole thing was, how much they disagreed with it, whatever. Something like Pluto, demoting a freaking planet, should have been a long process involving the entire voting body along with others so that a genuine consensus and agreement could have been reached. Instead the IAU came off, looking like fools and rapscallions with an agenda, making a significantly unpopular decision among the average joe, and causing embarrassment when the infighting and underhandedness was revealed and those who disagreed made their feelings known to the press.
All around pathetic and horribly handled. Tyson's casual dismissal and arrogant condescension to any who disagreed just added kindling to my dislike for the man as the face of modern astronomy. Even if you agreed 100% with the decision, a reasonable person would concede it was a disaster and a mistake to have been done the way it was. Likewise, this pales in comparison to idiocy like 'ice fishing on Europa' and wanting to 'kiss a Europan fish' or whatever it was he said.
Oh, one more bit - I was going to conclude that I don't care about the IAU's decision and that when New Horizons visits it in another couple years, we'll be looking at the ninth planet as far as I'm concerned. By the by, I know I've said this before, but New Horizons is going to be an amazing mission. Look up the best images we have of Pluto from Hubble - a tiny dot. Then imagine we've sent a probe all the way there, and will be getting data and images up close and personal. The final piece of a solar system tour begun with Voyager and the Venusian and Martian missions from the 60s-70s.
But NH makes their decision that much worse. Instead of being able to promote it when it arrives as the final planet revealed, a miraculous and ambitious mission to the outer limits, the demotion diminishes the headlines and possible interest and support for future missions that NH might have engendered. Beyond the cheap way the IAU did it, even if it had been handled right, they should have waited until after NH. To do so after the mission had launched and was well on it's way shows disrespect to the folks who worked on it as well as hurting the cause of public awareness/support for astronomy. There was just nothing about the demotion that was done correctly, and so Tyson's absolute disregard for objections especially in light of NH is all the more grating to me as an astronomy geek and passionate advocate for the future of human exploration.