Personally, I couldn’t care less what other men and women do viz-a-viz marriage, but I do object to adult men “taking” very young women as their wives. And that seems to be what usually happens. I am glad we have these laws if for no other reason than to protect young women from being sex slaves to these pedophiles. Look at multiple marriages in other cultures–you don’t see many caliphs or whatever they’re called with 12 old women surrounding them–there may be one or two older ones, but they usually treat the young ones like slaves, also. Please let’s make this clear–there is no room in American culture for this kind of slave-trading.
Um…OK. I’m with you on the “no slave trading” thing. But when you say “very young women,” are you talking about young but legal adult women? Or actual underage children? Adult women in our culture can pretty much do what they want, even when they are still young.
I, or I would if I followed the Rule of Seven religiously, which I would were I single and the opportunity, against all odds, would present itself, though women younger than that have so little in common as to be uninteresting; however, I know women who violate that rule . . . .
What was the question, other than, “Is she younger than my oldest daughter,” which is hard to explain? 
The OP has a habit of posting responses to columns without providing a link (or any other reference) to the column he or she is discussing. And then never returning to the thread.
The column in this case is What’s so bad about polygamy?
Heinlein presented some alternatives to traditional marriages in “The Moon Is A Harsh Mistress” and I believe in some of his Lazarus Long stories. And they weren’t the usual one husband/several wife kind.
What a crock.
Marriage below a certain age is illegal now for anyone. You don’t have to ban polygamy to enforce that law.
But this is disingenuous. Polygamy is associated historically and in practice assaciated with under-age age-disparete sex. Enforcement is difficulty and unsuccessful. Like the war on drugs. I can sugest reasons why that is so, but I don’t have to: I merely observe that it is the case.
*I have a religous position on polygamy: in my tradition, polygamy (including serial polygamy) is specifically prohibited for people in leadership positions