That all in itself, even if we disregard polygamy here, sounds like a very dated interpretation of marriage to me, at least in that radicality. Which of course would mean there is some truth that marriage laws might need to be rewritten...
That's the legal
effect of marriage. The creation of a legally-recognized family unit, and the effects of that on taxes and obligations. And I agree that the marriage laws may need a rewrite.
If the government doesn't recognize it is in fact not a marriage. Marriage is foremost a social/legal construct and only secondarily religious. Unless of course you mean the states with "you can do whatever you want", i.e. letting the states recognize it.
Au contraire. You can have the legal aspects of marriage stripped out and still have the social aspects, so long as the government is not actively interfering and banning the marriages. (Also, I find it funny how you argue with me for stating, as I did above, the legal effects of marriage in our society today, and then you turn around and argue that the legal aspect of marriage is the primary one.)
I think it's perfectly valid to laugh about deontologic ethics.
You're entitled to your opinion, no matter how wrong it is
On a more serious note, I'll say that religion is not any less
valid than any other source of values (which is to say, they're not, but neither is anything else).