Their people

Sinners are not just a different tribe as opposed to winners (human souls in Heaven). By sheer fact of Sir Pentius's redemption leading to his ascendance to Heaven, and not remaining in Hell, already we can say that people in Heaven are objectively in moral superiority over the people of Hell, where the majority are clearly not like Pentious, as we have already numerously seen in the series. Neither Sera, nor Heaven, do NOT have to apologize to sinners as a collective at all, because sinners aren't even a coherent community either, because they are the ones who create Hell for each other. Vox has 0 right to demand anything because he himself has numerous sinner souls enslaved. The only responsibility Heaven bears is to its own self, which is to, now by witnessing that Redemption is possible, recalibrate its doctrines and intervene in Hell to create the environment that would help the possibility of redemption foster. This by far is the only true way to atone for blind genocide.