Social justice requires irreligion; the reverse is true as well. Men need to feel they live in a comprehensible world. If God’s running the show then that’s taken care of, so government can become a matter of what is practically expedient in a situation that is fundamentally well-ordered. Perfection of outcome is not needed because perfection has already been attended to.
If there is no God, then we must create order. Since it is the order of the world as a whole that concerns us most—it is that order that lies behind all thought and action—the death of God means that man must become, as a practical matter, divine. He must construct the world as an ordered system, and since he can’t rely on any higher power or tendency of things toward the good, he must do so as an act of will and by force.