The ten commandments did not encourage promiscuity.
And what's your definition of promiscuity? Is 700 wives and 300 concubines not promiscuity, but having two consecutive monogamous sexual relationships before you get married promiscuity?
Neither did any of the prophets from the OT.
They just practiced it, and then got cited later as examplars of human behaviour.
Jesus did not nullify or drastically redefine God's laws - He clarified them.
The editors who selected and adjusted the works now collected in the New Testament (and possibly their original authors, too) tried to redefine god from a spiteful, violent, genocidal, sex-obsessed despot into a nurturing, supportive, sex-obsessed gaslighter (with a thinly-veiled mafia threat).
And from your previous post you explicitly accused Christians of being encouraged to use sex slaves. By definition, Christians should be followers of Christ's teaching, so I do not see how you could say they were encouraged to do this.
Gods rules for his chosen people - are you not his chosen people? Or are you suggesting that Christians are fine with Jews doing it, but they're not allowed to...? Either of those is an acceptance that it's sometimes acceptable, which I'd argue civilised people would disagree with.
O.