@BowsacNoodle @givenup @SuperLutheran Disclaimer: I'm not a Nietzche scholar. You'd be better off consulting EssentialSalts for a quick rundown.

But it seems it's not about accepting/denying reality, but the value judgements and moral demands placed upon reality.
Master morality says "it is what it is, and what is, is good".
Slave morality says "Actually, there's a transcendent moral law which says I deserve such and such from strong people and that strong people are bad for not following these rules."

Now, it is true that previous kings did impose a moral law upon their subjects, and maybe they interpreted as divine instruciton. But their relationship with the law is totally different as sovereign and subject.

It helps a slave to simply obey and accept, whereas a king or barbarian must discern and proact. It helps the slave to say "I get raped and beaten by the guards, but I deserve it because the king is good and I'm a bad goy." He has no way to change it, so it's easier long-term to accept it as moral punishment and turn himself into a little bitch. Christianity just supposes a bigger, badder king with worse punishments/better rewards in the hereafter.
A king, a sovereign, someone with the power to act, is helped by "rules are just made up and I can bend them to achieve my goals". The elites of our time are immoral because it helps them dominate, and we hate them because we ain't them. If we had a protestant calliphate, you bet your ass we would be doing some heinous shit because "the ends justify the means".