For me personally with having two wives, I've had far more push-back and hatred from so-called Christians than I've had from non-religous people. Religious people have been worse by far.
It is my speculation, my hypothesis, that majority of Christians that you describe who would give you push back would be from a camp that deviates from true message of the gospel: Catholics, Orthodox, and Calvinists. I would be surprised to hear if someone outside these camps I listed would
anathematise you for polygyny. I am sure there are exceptions, but general tendencies. (I understand some of you may still put yourself in this camp, but it is my observation, I hope to start thread about this later). And by anathematising I mean they would claim that you do not possess the salvation and will deny you fellowship with them.
It appears that true things about God would be more palatable/acceptable including polygyny if the gospel produced new creation. Christ said the following,
"He that is of God heareth God’s words; ye therefore hear them not, because ye are not of God"
And in the same place, "Ye are of your father the devil, and the lusts of your father ye will do. He was a murderer from the beginning, and abode not in the truth, because there is no truth in him. When he speaketh a lie, he speaketh of his own, for he is a liar and the father of it.".
One of the great things about living in liberal societies, is that religious zealots with false gospel are limited in carrying out their self righteous condemnation. As attack on Münster of 1534–1535 testifies about that.
So I would say in order for people to accept polygyny unadulterated gospel message should be shared and spread.
Regarding various camps I mentioned. I believe that in spite of false gospel being propagated in those camps, there are plethora of saved souls there.