Indeed. In Old Testament Bible times, men had more than one wife, but not the other way around.
Many people confuse religion with culture, using religion to legitimize their cultural or political position.
Let's remember that at one time in this country, it was legal to own a person.
Since we are a democracy, law is what the majority of people say it is. Morals, on the other hand, are something completely different, impacted by culture and law, but not quite the same.
My spirituality informs me that God cares not a whit about our combination of love relationships, the real issue is the love and pain (sin) we can cause those we love, or those we should not be hurting...and when people have more than one erotic partner, there is a far, far greater potential to let loose such pain.