Let me go on the record as saying that Disney was deceptive with this film; it is inappropriate for anyone younger than 12 and possibly 13. This is generally because it's a mixed bag.
First, the positive. Quasimodo and Esmerelda are positive role models whose values kids would do well to imitate. Esmerelda's song on behalf of outcasts will make you cry, and there is a great nod to Jesus in the lyrics. Phoebus shows a lot of growth for a Disney character, though he can be a bit of the classic "shallow jock" type. There is also a wonderful overarching message that "monsters" aren't always who and what we think, and that the church is meant to be a sanctuary, even though some use it for sinful purposes. (The archdeacon is a lovely example of the positive side of this). Quasi's gargoyle friends provide good comic relief, as does Clopin.
Now, the negatives. Claude Frollo is my least favorite villain, because he is a monster--one wearing the cloak of Christ. His attitudes toward disability, faiths other than his own (Roma Gypsy), and people who he believes to engage in any type of sin, are reprehensible. This man doesn't understand mercy or true justice, and for that, he is a frightening, overly dark animated villain. If his darkness stopped there, I could probably recommend this film for a slightly younger audience. But the fact that he very vocally lusts after Esmerelda, sings of her burning in hell, and violently attempts to kill her (among other characters, including a baby) pushes him way over the edge.
One minor note: In the context of this story, it may not be necessary for Christian parents to spend much time on the fact that Esmerelda's religion, which centers on occultic practices like palm-reading, can have its own darkness. In fact, it may not even be advisable, as the point here is that no one should be persecuted for any faith. But depending on your child's impressionability, you may want to discuss implications if your house does not condone palm-reading, fortune-telling, and its ilk. (A good explanation might be, "Some people believe in this, and you can treat them kindly and ask questions. But we don't believe in this, and we don't do it in our home. If you have questions, talk to me or an adult you trust.")
Keep younger kids out of this cathedral--it's way too high for them. But for older kids and adults? Proceed with caution, and be prepared for good discussion if you watch.