There were environmental arguments presented against stacking rocks, and there is nothing lost to an individual by not stacking rocks. There is no hunger or suffering involved by abstaining from that, but the counterpoint was, apparently, "DONT TELL ME WHAT TO DOOOOOOOOOOOOOOO."
:manhattan:
The general idea behind "leave no trace" is that ecosystems and biomes are very fragile, and everything we do, bring and leave behind when we go into nature fucks them up. Some stuff, like chemicals from soap or micro trash plastics, do even MORE harm than stuff like apple cores or your morning shits
Basically, you want to act as close to the time travelers from "sound of thunder" as possible