If you prohibit arguing about the shape of the Earth, you're banning people from explaining that EGM08 is generally more accurate than EGM96—and where it isn't. That is a significant harm. Trolls advocating obvious nonsense like flat-Earthism isn't a significant harm, because nobody over the age of 6 will be misled.

Even if you were right that debate on the shape of the earth had no benefit, forbidding it still wouldn't be science. Science is not coextensive with beneficial things.