You guys are always trying to use arguments that are false analogies. Plural marriage is not analogous to same sex marriage, not at all: it's a completely different thing. One marriage: two people. That's the traditional way and the same sex way. Plural spouses is not at all the same thing.
Ok, let's examine it then:
Prior to same sex marriage becoming law, a requirement of the license was that the participants be one woman and one man, not too closely related.
Why did that requirement exist in traditional marriage?
The answer is that it made it impossible for bloodlines to produce defective children or defective children in future generations, due to inbreeding.
That argument has zero merit when we speak of same sex marriage, correct?
The limit of two, was connected to the limit of "not too closely related", so the number is arbitrary.
The argument against plural marriage is based on several issues, none of which has merit in same sex plural marriage.
It allows males dominance over females? In an all male plural marriage? How so?
The biological relationships of the children in a all male plural marriage? HUH?
None of the arguments that were reasonable with opposite sex marriage, have merit with same sex marriage as it relates to many forms of incest or plural marriage do they?
Now, how do you exclude straights from these, when you have no compelling state interest in the denial of this "right" to same sex couples?
We have that Equal Protection laws and the right to due process that seem to indicate that you can't discriminate based on one couple ability to procreate and the others inability.
Remember, I did not create this argument, it was actually created to support same sex couple rights to marry.
Don't blame me, I have been arguing for years that removing the limiting factors in marriage opened the doors to all.
Same sex marriage will either implode or force states to end the institution.