Pluto's demotion is a great opportunity for science

This article makes an excellent point. I can only speak from the US perspective, but I think a lot of the reason the average non-scientist has trouble with things like pluto suddenly not being a planet anymore is the way science is taught to us as kids. For the most part, everything in science is presented as a nice tidy package with little ambiguity as if we have it all figured out. Sure, you get the occasional "scientists don't understand XYZ yet" sort of explanation here or there, but for the most part everything is presented as settled. This presentation persists from the time kids are very young, all the way up through high school.

As a scientist, training yourself to be objective and questioning is one of the hardest skills to learn. It takes until college before you start realizing that science is messy and has all sorts of caveats, controversies, and disagreements. Some of the issues are presented to students, but they are often the ones which are blindingly obvious now (i.e. we have confirmed to 99.9% certainty that the sun does not revolve around the Earth). Rarely are the really dicey controversies presented.

It takes even longer for you to realize that not only does all this ambiguity exist, it's actually the norm. Once you start looking back at history, you realize some of the biggest scientific discoveries were based on people saying, "what if all my assumptions are totally wrong and there is a completely different explanation for what I observe?". Or, some new kind of technology enables you to view some previously hidden phenomenon and all your assumptions are overturned immediately.

Unless you actually pursue a science-related career, you unlikely to ever really understand any of this.