Can I draw a parallel from what the French gov't is doing to how the US gov't forced the Mormon church to abandon their practice of polygamy? Would that also be a case of the dominant culture trying to oppress a minority culture?
That raises the question of why the government is sticking its nose in marriage to begin with.
Practically? I think its tax related. The tax code is fucked up as it is. I can't fathom coming up with different tax codes for man who wants to marry anywhere between 1 and many wives. (or one wive and many husbands)
But are you raising the point just for the sake of argument or are you actually for polygamy?