I agree. But there is always that small percentage (probably very small) that would demand this. Do we have to listen to their arguments if they go to court?
To be honest, I am not even trying to argue this or anything else. Just playing more of a devil's advocate to people who seem to think that now, hopefully, the gay marriage issue is settled and there are no more marriage arguments to be made. There will be. There are already polygamy issues in Canada.
Absolutely, there is no harm in listening to their arguments and arguing back.
What people sometimes don't realize is that Courts often have to listen to two strong arguments, and apply the law and/or the spirit and intention of the Law, and sometimes, find such laws to be unconstitutional or unlawful.
Those are complex cases. However, when you have a weak argument against a strong argument, and many laws spanning different aspects of life apply, the weak arguments don't hold water.
I can stand here and give arguments for Polygomy (I love playing Devil's Advocate, it's a strong tool for gauging the strength and validity of your own position, or arriving at a novel position), but I have to say, they are not strong at all when you apply the tests that courts will use.