You're right, it's more promiscuous that polygamous.
Actually I don't have a problem with either as I believe a sexually liberated society is a society less prone to perversion or sexual misconduct.
As for me and myself, MY behavior is more conservative as I believe children should only be produced within the confines of marriage to people who are financially stable enough to support them, but I wouldn't force my personal values on everyone in society.
I'm a personal conservative who believes in a liberal society if that makes any sense.....lol.
I just ask that people be responsible in whatever behavior they choose to engage in practicing safe sex to prevent the spread of disease and taking care of any children that they produce.