Pluto was a planet, once. The crown jewel of the Plutonian Empire. But the Plutonians got greedy. They dug too deep in search of plutonium and awoke a terrible horror. Now all that's left of Pluto is a cloud of asteroids and a celestial dwarf, barren and uninhabitable.
The problem with Pluto being a planet is that we would also have to classify something like thousands of other objects as planets as well. That's the whole reason it's not classified as one anymore.
People are only mad about Pluto because it happened in their lifetime.
Prior planets include The Sun, Ceres in 1801, Pallas in 1802, Juno in 1804, Vesta in 1807, Astraea in 1845, Hebe, Iris, and Flora in 1847, Metis in 1848, and Hygiea in 1849.