No... Christianity does not condemn anything. We are talking about God.
There is no command concerning prostitution, or porn, but they are lusts of the flesh. And adhering to the anti-fornication doctrine, One wife/one husband is a willful submission. A return to the garden by accepting the truth in regards to walking in the fulness of the Spirit, with our whole heart, like all the other prophets, priests and kings.
Polygamy is contrary to the character of God. The only command in the OT with polygamy in mind is: "Neither shall he multiply wives to himself, that his heart turn not away..." The word multiply means to make many... which relates to being plural which is more than one. It is not the sole definition, but the OT makes a point of reiterating those who had "two wives." This commandment is written in regards to kings. With God there is no respect of persons, so what's justified for the king, or Abraham, becomes justified for the least of all the servants of His kingdom.
The condition of having two wives seems to lead to more in the OT even concerning David, who was after God's heart. It also contributed to sibling rivalries that ended in division of the kingdom and it's allegiance. So it's no surprise the Spirit would illustrate fornication as a result of polygamy, this by no means calls it commandment, or law, but shows that the better fruit is in the kings fruit bowl, so we should live like the king of kings and have one bride.
This is not to be confused with the law, or commandment concerning polygamy, but the Spirit witnesses for itself that it is a detriment to walking before God with a perfect heart, so it is of the flesh. Just as Jesus intensified adultery in His sermon on the mount, "That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart."
The Christian position is that we are a royal priesthood, heirs to the king, therefore the kings law is kept by the Christ in us.