This has always struck me as one of the lamest anti-science arguments out there, and it surprises me to see it coming from such a thoughtful poster as yourself. This would only be an example of science being "wrong" if the change was due to our knowledge about Pluto being wrong, or if there was some objective standard of planetude that we were wrong about. In fact, though, it was a simple definitional change: astronomers defined "planet" in a certain way (there was no official definition before) that lumped Pluto with 40-odd other, similar, non-"planet" bodies rather than with the 8 "true" planets. Nobody was wrong about anything.
Science rarely elevates a theory to a "law" and instead speaks of evidence accruing for or against theories. Ditto for taxonomy whether classifying a planet or a fossil.
And some theories which remain good in one context fail in another - e.g. Newtonian physics v. Relativity v. Quantum Mechanics.