Snuff Out is a cheap answer to the things that matter here: Hermit Druid (a nonblack 1/1 engine piece) and a Phyrexian Dreadnought (a colorless, so nonblack, 12/12) that sticks around, for example when they Stifle its sacrifice trigger. It can't hit their black Sutured Ghoul. Sickening Dreams is unreliable since their deck is mostly engine pieces (Hermit Druid, Lotus Petal, tutors) with only a few real creatures, and it costs us cards and damages us along with them. Keep our full discard suite (Duress, Unmask, Cabal Therapy) since stripping their Reanimate or Vision Charm before they can reanimate a Sutured Ghoul or protect a Dreadnought is critical. Our own Reanimate and Exhume plan races well if we can answer their one big threat with Snuff Out.