With POD(s) after 1900, have polygamy in the western world be at least as acceptable as homosexuality, LGBT rights and such are in OTL 2013 western countries. It can still be outlawed/persecuted in some areas of the world...
But make it quite acceptable to have several wives (and/or husbands) in the western world, so that those that are against it might easily be labeled "polygamophobic", "arch-conservative" or something else.
But make it quite acceptable to have several wives (and/or husbands) in the western world, so that those that are against it might easily be labeled "polygamophobic", "arch-conservative" or something else.