God is just and right in all His ways; Deut 32:4. He cannot do bad or wrong in any way. God is holy, which means He is separated from all immorality of any kind. Moreover, He is hostile toward sin. When God sees any sin or evil, it stirs His wrath and anger. Fire seems to be equated with holiness. God is called a consuming fire; Isaiah 6:3, Habakkuk 1:13, Exodus 3:2, 4,5 and Hebrews 12:29. God does not change His character. He is immutable; Psalm 102:23-28; Malachi 3:6; Numbers 23:19; James 1:17; or as Hebrews 13:8 states “He is the same yesterday, today and forever.” God is Holy. He cannot abide anything bad or wrong then or now. God's measure of acceptable is perfection.
When we question practices that God required and participated in and call them bad we call God's character into question. The slippery slope here is that as a general rule the modern Church condemns something God instituted in His law. God required polygmay in circumstances.
Duet 25:5-10 required polygamy as part of Levirate marriages.
God delivered Saul's wives to David 2Sam.12:7-8 and it is implied that God would have given more to David. God participated in the proliferation of polygamy.
There were limits on it in the law like not marrying sisters, mother and daughter. Inheritance laws in cases of multiple wive were covered. Concubines distinguished from wives were accepted and protected although differently, under Mosaic Law Ex. 21:7-11; Dt. 21:10-14.
Mosaic law was given by God to Moses. God is perfect and cannot tolerate anything less than absolute holiness. This forces us to rethink cultural values that we have today compared to God's unchanging character.