For the record op her name is Brunhilde, not to be confused with the long running comic strip "broom hilda" of a similar name likely an allusion to the same opera character.

On that note, he's likely an abolitionist but that's not the focus of the story at all, even if it has parallels. There's certainly plenty of animus from the main cast for how the slave owners terribly treat their slaves, but while that might be related to abolitionism it's not exactly the same thing.