You have a good pont. However as you stated, being legally ‘married’ is not a valid way to establish legal paternity. I agree that a child has a right to paternal identity, and it is indeed a troubling issue. And I also agree that the government does have a role in establishing ‘fatherhood’, and to some degree, enforcing the responsibilities that go with it.
However, being ‘married’ or ‘unmarried’ does not itself establish paternity with any validity, so it’s a seperate issue.
I still firmly believe that the government has no legitimate reason whatsoever to care whether a person is married or not, and it follows that nor shall it care to whom one is married. If a person wants to declare that they’re married to a fencepost, why should the government intercede?
In the US, even without "gay" "marriage" from sea to shining sea, we're already at the tipping point: over half the births to women under the age of 30 are already out of wedlock.
Since marriage by any definition is no longer the norm, does that mean the government must now carry through with the far more expensive, and far more intrusive, policy of administering DNA tests to all of a woman's ... er... male associates, upon the birth of every child?
Or, drawing back from that, do we just say, "OK, every child is now a half-orphan: a paternally abandoned child. We've given up. First, no more legal wedlock. And now, inevitably: no more legally enforceable children's rights."
This is not a trick question. I'm asking.