Kudos to Topher for recognizing which sub-forum he’s responding in!
It was never “OK”, and an approach which fails to distinguish between approval and toleration is going to miss the point. A lot of things are tolerated which are not actually OK (approved). Christ pointed that out over the question of divorce. Divorce is NOT “OK”. It was tolerated under Mosaic law because of the hardness of our hearts. But it was not always so. The intent from the beginning was monogamy. Everything else is sin, falling away. Even when it was tolerated, it didn’t end well in the stories passed down to us. Abraham SHOULDN’T have taken Hagar to his tent; he should have had more faith in God, and evil was born of his lack of faith. Adam and Eve SHOULDN’T have partaken of the fruit in the garden, and NO one “should” get divorced or accrue multiple wives. Ever. At any time in history.
The Christian ideal calls us to live as we SHOULD, and does not approve of even what it may tolerate. And as we SHOULD is hard. But that’s what we’re called to. We’re not supposed to be looking to see if something is “OK”, if we can get a free pass, a “Get Out of Jail Free” card. And the ancient Jews weren’t actually supposed to be doing that either. They were supposed to be seeking to live by the Word of God. And they didn’t, not as they should have. Not Abraham (and thus he needed his faith to count for righteousness), not Solomon, who managed to completely fall away in consequence of his uncontrolled appetites and political ambitions, none of the Biblical polygamists is approved in their polygamy.
The Christian should understand that marriage is an icon of Christ and His Church, among other things, and that that relationship must be kept exclusive, holy, and faithful. That removes everything that violates that from the list of what we should be OK with, and that includes both polygamy and divorce. That doesn’t mean that we should condemn others for their past sins, any more than we want to be condemned for ours, but only that we should live ourselves, and encourage those Christian brothers and sisters who do think we ought to obey and take up our crosses, and love our enemies, to uphold and carry them from now on, whatever we may have done in the past, be it fornication, adultery, polygamy or divorce, precisely because they are not, and never were “OK”.