The God of Abraham, Isaac and Jacob can do no evil. He can do no sin. That is a part of His very nature. If having more than one wife is evil then Yahweh God helped David to sin. Yahweh spoke through Nathan the prophet to David in the following verse.
God Gave David His Wives
2 Samuel 12:8
"And I gave thee thy master's house, and thy master's wives into thy bosom, and gave thee the house of Israel and of Judah; and if that had been too little, I would moreover have given unto thee such and such things."
So here we have God telling David that he would have given David more wives if he had asked for them.
Oh, but that was for the Old Covenant some will say. This would take the discussion into the Law of God. There are several articles on that subject at Oracles of Yah.
Feel free to send your helpful comments.
Basic Articles on Marriage, Children, Divorce, Remarriage and Adultery
Articles on Polygyny
Scriptural Marriage Possibilities
Polygyny is not Adultery!
Who did Seth Marry?
Lamech Had Two Wives
A Damsel or Two.
God Gave David His Wives.
How Many Wives per Man in Israel?
Is Polygyny Still Righteous Today?
Is Polygyny a Blessing from God?
Is Permission for Polygyny Required?
It Began with One Man and Four Women
Let Each Woman Have Her Own Husband
Hosea's Two Wives
Is this the Meaning of Leviticus 18:18?
Women with Women?
Men with Men?
Support for Scriptural Polygyny
How I discovered Polygyny
Sunday Morning Visitor
Poly Friendly Book Reviews
Christian Polygyny Links Page