Saying Pluto is not a planet is a sure-fire way to make children angry. When the Hayden Planetarium in Manhattan excluded Pluto from its list of planets, children protested. Loudly. And sometimes to planetarium director Neil deGrasse Tyson himself. The PBS show NOVA compiled a few samples of the hate mail, including this gem from Madeline Trost of Plantation, Florida:
Why can’t Pluto be a planet? If it’s small doesn’t mean that it doesn’t have to be a planet anymore. Some people like Pluto. If it doen’t [sic] exist then they don’t have a favorite planet. Please write back, but not in cursive because I can’t read in cursive.
Source: NOVA