Why is polygamy/bigamy is considered a crime in the west?

-Coz much of the west is grounded in Judeo-Christian civilization wherein is it taught that man should only have one spouse. laws are guided by this guiding principles set by the bible.

Prostitution, same-sex marriage, adultery, and the likes are sins which are now eating away the morality of the west bcoz they have turned away from the God of the bible.