It was practiced by many early Christians as well.
Only in your imagination. You never produced any proof for this.
Many people from our Bible were polygamists.
Just for clarification, this is not a wife with multiple husbands. This is a husband with more than one wife.
Remember the Samaritan woman? She wasn't practicing polyandry (being married to more than one man at the same time), but even so Christ told her the man she was with wasn't hers. The biblical definition of what a relationship between man and wife ought to be is this: Ani ledodi vedodi li = 'I am my beloved's and my beloved is mine.' (Song of Songs 6:3), which is also the mystery of Christ and His Church (Ephesians 5:32). This is absolutely reciprocal - no double standard for men and women.
But biblically, I don't see the crime, unless you are a bishop.
The priesthood was always held to a higher moral standard, but Christians are supposed to be a "kingdom of priests":
They must not marry women defiled by prostitution or divorced from their husbands, because priests are holy to their God. Regard them as holy, because they offer up the food of your God. Consider them holy, because I the Lord am holy—I who make you holy.
The woman he (the High Priest) marries must be a virgin. He must not marry a widow, a divorced woman, or a woman defiled by prostitution, but only a virgin from his own people, so that he will not defile his offspring among his people. I am the Lord, who makes him holy.
And this you do as well: You cover the Lord’s altar with tears, with weeping and groaning because he no longer regards the offering or accepts it with favor at your hand. You ask, “Why does he not?” Because the Lord was a witness between you and the wife of your youth [SINGULAR, mind you!], to whom you have been faithless, though she is your companion and your wife by covenant. Did not one God make her? Both flesh and spirit are his. And what does the one God desire? Godly offspring. So look to yourselves, and do not let anyone be faithless to the wife of his youth. For I hate divorce, says the Lord, the God of Israel, and covering one’s garment with violence, says the Lord of hosts. So take heed to yourselves and do not be faithless.
I wonder how you understand this passage: is a man bound by covenant only to "the wife of his youth" whom he may not divorce, but he should pass for faithful if he takes as many women as he can support beside her?
Why do I have to prove history to you?
Google out "Early Christian Polygamy", or read Eusebius's lost work. This is historically common knowledge.
You quote song of songs, which is often attributed to Solomon. He had many wives. This is not in context with the mindset of polygamy. The wife is his, he is is wife's, but he has several wives. - This is a Polygamy mindset.
I don't see how discussing women's virginity has anything to do with polygamy. If she is a virgin he can marry her. If later he finds another virgin and wants to marry, he can marry her.
You quote "The wife of your youth" noting it is singular. You need to research polygamy better, as men who marry multiple wives typically don't marry all of them at once. The wife of somebody's youth very well could support polygamy, as more wives come later in life.
On a side note, in today's world, I totally see there may be a need for polygamy again, especially amongst Christians. I am seeing in almost every church the female body of the church being about 33% larger in attendance than males. Many women come and say "I wish my husband would". It's sad. Lots of single mothers that are Christians looking for a good man who is a Christian. If there is an 18 year old girl with a child, and a married couple with children who would accept her as a sister-wife, and give her a stable Christian life, supper at the table, a home, and love, I guess I would support it. And why not, many 18 year old men (or close in age) don't want to marry an 18 year old girl with a child already.
Usually those types of girls have to "settle" for a 40 year old perv that wants to boss her around who has already had a divorce. I'd say it's better she marry into a stable family with good support an values.
Sorry my friend, but Polygamy is part of early Christianity no matter how much you want to cover it up. I do not see it as a sin. Canon (men's canon) states otherwise. This is a subject I've done a very in depth study on as we knew Mormons who practiced it. The conclusion from the study is that it was practiced by some (moderate) early Christians, but not everybody.