This brief article shows the limits of arguments against religious polygamy that are based on the Bible, tradition, public health, child welfare, or public policy. It instead argues that polygamy is a malum in se offense, something that is inherently wrong or too often the cause, consequence, or corollary of wrongdoing. Polygamy cannot be countenanced in a modern democracy, even if it is pressed on religious freedom grounds. The author has developed these themes at length in The Western Case for Monogamy over Polygamy (Cambridge University Press, 2015).