Never conceptually from biology which is the heart of the issue which is the definition of family. Ersatz methods of reproduction does not obviate this simple truth. 

you have to be more specific then that. why and for what?

We do not live in a religious theocracy or a fascist autocracy so one group does not get to oppose their views upon everybody else. There are many cultures and religions that traditionally allowed same-sex marriages and the number is growing by the day. People like yourself should have no right to deny other cultures (like our own Native peoples) and other religious organizations what they can and cannot do. They do not care about your need for a couple to be able to "CONCEPTUALLY reproduce" because it is an asinine criteria. If being "natural" is so important to you maybe you should reconsider participating in an extremely unnatural civilization.

A politically neutral state has no legitimate interest in granting marriage licenses to a non-natural family. Same sex couples don't need to marry. There is no logic or reason other than some pseudo-spirituality about love. 

Unless that neutral state's mission statement is 'life, liberty, and the PURSUIT OF HAPINESS' for it's citizens.  Granting all citizens equal rights and protections under the law is a rather important function of such government.  There is absolutely no legitimate reason to deny gay people the right to marry.  And no, 'reggin_bolas' thinks it's 'icky' is not a legitimate reason.

According to who exactly? The "traditional" marriage I see so many trying to push on others originated as a Jewish ceremony in which women were effectively sold into slavery. I could rape a woman and then exchange property to buy her (as long as she was the same race as me). Could you tell me exactly what version of marriage you think should be forced upon every nation and all of their peoples? Can you clearly define it and reveal its archaic origins for us to dissect? If you are such a staunch supporter of "traditional" marriage would you mind discussing your views on interracial marriage, arranged marriage and divorce?

Interracial marriage is neither natural nor supported by "traditional" marriage.

Same-sex couples are denied a bevy of rights and privileges when excluded from marriage, thus they do in fact need it.

There is no logical reason to enforce one religion's views on marriage in a secular nation beyond some pseudo-spirituality about "morality".

I never once mentioned a traditional marriage. Nothing is unnatural about interacial marriage. I have no problems with divorce. Arranged marriages? It's not relevant to the consitution nor to the entire debate. The only thing at stake is the definition of family which marriage aims to protect. Man and woman is the only cross-cultural and thus universally accepted definition of marriage. All other things such as arranged marriages and age of consent vary from culture to culture. 

What of those adopted by gay couples?  Are they not a family that should be protected to insure the safety and well being of future generations?

And guns for unborn babies. They have the right to life, and dammit they need to defend themselves.