Now that griffons and dragons were brought into it, I can't help but wonder about the alicorns. Celestia's the one making all the laws, so she would have the power to make herself immune to them. She and Luna are quite possibly the only ones who could shit on any pony's head in public, declare it an act of punishment for a crime they made up, and no pony could say a word to them. Sure, it wouldn't be in their character to do something that low. But if Chrysalis or some other villain had the means to brainwash them into doing it, well, that's a problem that would quickly escalate to every lowlife being inspired to follow their example. With ponies thinking, "If the princesses can do it, so can I!", Equestria would get covered in shit so fast, the economy would collapse over night.
That's actually worse when you think about it. I'm sure no pony wants to breath all that fecal bacteria floating in the air. That's what makes people want to throw up when they walk near a pile of crap or into an overwhelming fart. You can get sick regardless if you touched it or not. And even if that fireplace got cleaned, lighting it up would cause some leftover residue to spread the bacteria across the neighborhood. Then every pony would end up painting the roads with their own vomit, hence even more bacteria spreads and a new cycle of vomiting begins. Twilight would need a damned good spell to help her breath in Ponyville without catching diseases, because that's a lot of shit for her to clean up.