The Pink dog of the Night

So this poem claims to be a dog but I just kept seeing this prostitute that the church-going ladies of the town looked down upon (perhaps I took the word bitch to literary (in line 11)). So after they're done insulting this women/dog I found that this poem had everything, yet nothing to do with the dog. I think that this dog was used to show the terrible treatment of the poor in this population. I mean they're throwing them into the river, then saying that they have to dress up/disguise themselves from the crowd in order to celebrate. They make snitty remarks (like calling you pink and bald, I don't think my balding grandfathers would like that one bit) and tell them to wear life preservers. This treatment isn't fit for dogs (why this poem is about the dog), yet the mistreatment of the humans is terrible (why this poem isn't about the dog, rather it uses it to soften the blow). The tone of this poem overall is condescending towards the poor population, and honestly I would hope that anyone celebrating Ash Wednesday (so logically they're of a religious background) wouldn't be treating their brothers and sisters that bad. I guess confession was made for a reason.