Pretty much any group that's not actually harmful can find a place under the UU umbrella, but it's mildly interesting that this one would cause knee-jerk reactions. I guess it's the old association of poly- and hedonism.
Dunno why that's in my head right now, just a stray thought. I guess the slippery slope would be the fear that the UU's would be obligated to push for legal rights for poly relationships. It does seem like a difficult tangle of thorns to work with. You don't want to be the wife-swapping, swingers church.
Dunno. Dun even no why I'm thinking about this.