Some of the people placed in hell by Dante were placed there because of Dante's own bias against them. I think you can argue that Brunetto Latini who is in the Seventh Circle for violence, Pope Boniface VIII who is in the Eighth Circle of Fraud from simony, and Epicurus who is in the Sixth Circle of Heresy.
It is very interesting that Dante placed Brunetto Latini in hell because Latini was Dante's mentor in life. Not only is Latini in hell, he is placed with a circle of Sodomites. As far as scholars know, there is no proof that Latini was ever a homosexual. So by Dante placing him in hell, he is saying that he is better than his mentor, but he is also "exposing him" so to speak. Dante and Latini were close, so if anybody had known if Latini was a homosexual, it would have been Dante. This can be a scary thing because Dante is controlling Latini's life after his death. Considering there is no concrete proof of this, I think Dante could have placed him in the First Circle of Limbo, seeing as Cicero is in that circle and Latini was a follower of Cicero.
In my opinion, Pope Boniface could have been placed in the Fourth Circle of Greed because he was not above enriching himself. I believe that Dante placed him in one of the worst circles because he played a part in Dante's exile from Florence, so Dante has a sort of personal vendetta against him.
Epicurus was an Ancient Greek philosopher and founded Epicureanism. Epicureanism was still around during Dante's time. Although, it was not very popular, it was still considered a heresy. I think that, by Dante's criteria, Epicurus' followers should be in the Sixth Circle, but Epicurus himself should be in Limbo since he was lived about 300 years before Christianity was founded and many other prominent Greek philosophers are in Limbo.