Im sympathetic towards anti-natalism at times, but I think the equating suffering with inherent badness is kind of a jump. Obviously suffering doesn't "feel good", but feeling bad and something being metaphysically "bad" are two different things. Physical pain, which obviously isn't the only kind of suffering, still wouldn't have evolved if it was so necessarily "bad", but pain has both a practical purpose and potentially a "greater purpose", depending on where you want to go with that.
Anti-Natalism sometimes feels like it makes the same basic mistake that Utilitarian moral philosophy does, equating something "feeling good" as being the highest possible good.
Also im pretty sure Anti-Natal philosophy could and would be able to be used to justify an "omnicide".
Though still, as I said earlier, I am sympathetic towards it none the less.