How we cite our quotes: (Book.Chapter.Paragraph)
Quote #7
Nothing was more common in those days than to indict animals for sorcery. (VIII.I.53)
This little tidbit might just seem like a ridiculous aside at first, but it actually shows us how convenient is to accuse people of sorcery: people accused of sorcery can't really prove otherwise, can they? This is doubly true for animals, who literally can't argue in their defense—or even understand that they are being indicted, for that matter.
Quote #8
Jacques Charmolue, by shifting the tambourine in various ways, made the goat exhibit several other tricks with regard to the day of the month, month of the year, and so forth, which the reader has already witnessed; and, from an optical delusion peculiar to judicial proceedings, the very same spectators, who had perhaps many a time applauded the innocent pranks of Djali in the streets, were horrified by them within the walls of the Palace of Justice. The goat was decidedly a devil. (VIII.I.57)
There is definitely some hypocrisy involved when it comes to the mob mentality of a witch hunt. Basically, you can attach a supernatural explanation to just about anything if you feel like it. That's exactly the point: it's a matter of perspective. Without the accusation of sorcery, it's easy to see Djali's tricks as… tricks. The crowd, however, is more concerned with seeing the workings of the devil. It makes things more exciting that way. It also makes all of them feel safe. None of them has a trick-playing goat like that, so if a trick-playing goat is a sign of sorcery, then they're safe.
Quote #9
"At the moment when these thoughts were crossing my brain I saw near her a goat, a beast that one associates with witches. It looked at me and laughed. The noontide sun tipped the goat's horns with flame. Then I perceived the demon's trap, and had no further doubt that you were from hell, and had come for my perdition. I believed it." (VIII.IV.50)
It's convenient for Frollo that Esmeralda has a pet that tends to be associated with the devil (for its horns and hooves and whatnot; the devil was often imagined as being part goat). Maybe a dog or a pot-bellied pig would have been a safer option.