I would say that the one court that, upon meeting/making eye contact with you, either-
-Kills you for no reason
-Drinks all your blood, killing you
-Turns you into a fellow undead horror
-destroys your mind and consigning you to a psychic slavery and a slow death
isn't really worth saving. I would have zero moral scruples with the genocide of the Black Court, but there might be ramifications similar to the death of the Red Court, which nobody wants. So you might face opposition on that count. If your players are on the fence, just have some Venator who lost a loved one/family member/childhood friend to the Black Court detail some of their atrocities.