Well, I have a sense of humor and I can tell you this isn't funny, except in a laugh at people falling or laugh at how suprised they are when you call them names for no reason kind of way. Trying to pretend vampires are so evil you have to run around killing them while giving slavery a pass is just plain stupid. Slavery is as close to real vampirism as life gets. The book is a lot like True Blood, it doesn't realize that playing with the metaphor (vampirism) when the real thing (the genuine evil of slavery) is in the story substitutes a feebler image for a more powerful one. It is anti-art. (In True Blood, vampirism is the metaphor for homosexuality but the real thing is the gay characters.)
The author by the way tries to finesse the problem by turning the slavers into vampire protectors/employers/allies/etc. (I didn't read enough of that garbage to get the fine details, sue me.)
Vampires are not actually people, so that disposes of the objection the movie would turn Lincoln into a blood-soaked killer.
The idea that Lincoln really is some sort of blood-soaked killer is ludicrous. All we need is stuff about tyranny and violation of civil rights and we've got full-blown apologetics for slavery. Lincoln didn't start the Civil War.