I actually keep telling my brother it's only a matter of time before we get a poop Pokemon. I joke that there would be a legendary trio of poop, pee, and toilet.
There is a poop digimon and many digimon can do poop attacks. In many Japanese games, there are poop creatures or creatures that use poop as an attack. For example, in Blue Dragon half of the enemies in the game are some sort of poop. Some are even poop with twigs and leaves stuck in it, and stuff like that. In Monster Rancher series, monsters fart and poop on each other for attacks.
It is not uncommon for there to be poop-themed stuff in Japanese games. It is not as 'obscene' to draw a cute-looking poop as it would be in western society. But even in places like Germany there are poop plushies and stuff.
So I don't think it's crazy to imagine a poop Pokemon and I wouldn't quit playing because of a Pokemon made of something like poop. It's not any different than sludge Pokemon or garbage Pokemon.
"Earth is a silly place. Half the world has no clean water. And the other half has so much, they poo in it."