The pigs and sheep are capable of conversation but live in a pen out back, Rarity has eggs for breakfast and Pinkie cooks with eggs and butter, and Fluttershy mercilessly murders smiling fish so she can feed the ferrets under the bridge. I don’t think “pets” are the biggest unspoken moral ambiguity in the show anymore.
It’s a matter of perspective. The ponies aren’t so mean that they’d treat sentients as property, and most animals seem to be able to have conversations with ponies. So they aren’t “pets,” they’re “guests” and whatnot.
Cats aren’t pets. Cats have food machines that they let live with them.
The sheep don’t seem to object much, they were mostly just annoyed.
There is no evidence of the pigs talking, and chickens and fish aren’t sentient either (besides is she just gonna let the ferrets starve?).
And eggs? Equines sometimes do and need to ingest protein, and besides chickens aren’t fully sentient either.
Things change over time. And the Mane Six having pets isn’t a bad change at all, not worth the whole “smack a bitch” reaction about it.