I was going to write about how baffling I found the opening to Unscientific America, the much-discussed book by Chris Mooney and Sheril Kirshenbaum, but Jason Rosenhouse said almost exactly what I had in mind. Neither of us can understand what Mooney and Kirshenbaum think astronomers should have done differently. Decided Pluto's status on the basis of a poll? As Jason points out, the only logical choices were either to demote Pluto or to promote many similar objects to planethood. Neither would satisfy the "nine pickles" crowd. And would we really want to decide other scientific questions with a popularity contest?
I haven't read Neil deGrasse Tyson's book (Amazon, B&N), but I found Is Pluto A Planet? (Amazon, B&N), by David A. Weintraub, to be very illuminating, (especially considering that the answer should contain exactly one bit of information!). He describes both the rise and fall in the number of "planets" through history--which make the number nine look quite arbitrary--and the problems with various objective definitions of "planet." Definitions that include Pluto also include numerous other smallish, irregular objects with inclined eccentric orbits, and in one view Pluto is the founding member of athis new class. Weintraub also reviews how Pluto was discovered in a search for the orbital anomalies of Neptune that turned out to be erroneous and in any case much too big to be explained by the pull of tiny Pluto, so that it should never have been promoted. But I won't give away which of the two "answers" he comes to. It's a measure of how good the book is that I still respect it although I reach the opposite conclusion.
But none of this explains why Mooney and Kirshenbaum think Pluto matters.