Cripes
If two adults of the same sex want to engage in consensual sex, its none of anyone else's business. That has nothing to do with either bigamy or polygamy - which has more to do with the legal status of marriage than it does with sex.
Consenting adults should be able to engage in whatever variety of sex they so choose. But marriage is a specific kind of legal entity that has nothing to do with sex.
Mr. Santorum has confused the activity of sex with instituttion of marriage.
Perhaps he should refill his Viagra prescription.