Death camps and firing squads are weak sauce compared to the ultimate weapon of mass obedience: social ostracism.
Repentance: once a means of righting your wrongs before God, now a mechanism for the savages of our post-Christian society to publicly humiliate anyone who goes against the grain.
If you’re a rebel and the masses can’t kill or silence you, their fallback is to try to convert you. Castrate you, lobotomize you, make you as mindless and suppliant as they are.