Nobody is being singled out.

If a polygamist's six wives came to the pastor of a Catholic parish and requested that their deceased husband be buried by the parish and demanded that all six wives be named as co-widows during the mass and listed in the obituary, he would be obliged to refuse too.

The only difference is that the polygamist's wives would have enough common sense to know the pastor would be obliged to say no. And if they were really Catholic, they wouldn't try to instrumentalize the Church's liturgy to promote a political agenda.