Spirit children of God

As one of the (many) reasons that gay marriage should not be sanctioned, I have heard the following argument.  "There are many of our Heavenly Father's spirit children waiting to come down to this Earth to receive a body.  I want to help them in this wonderful plan that God has made for us.  I can do that by providing bodies for them (ie, having children of my own).  Gay couples cannot reproduce, so they cannot contribute to this wonderful part of God's plan of bringing spirit children down here to Earth to get a physical body."  This post is my reply to that argument.

First, I ask a question to one who would propose this argument.  I ask, what is your motivation in providing physical bodies for these spirit children?  Is it greed, because you expect to receive some reward from God for doing His will?  As far as I can tell, the answer most would give to this question is "no".  Then, is it out of a sense of duty?  (You feel that you owe it to God to do what He says.)  I would say that perhaps some would reply affirmatively here, but still most would say "no".  Is it, then, a truly altruistic motive?  Are you truly concerned with the welfare of the spirit children of your Heavenly Father?  I will continue with my argument under the assumption that your answer to this question is "yes".  I will assume that you truly just want to help His children along their path back to live with Him in the Celestial Kingdom.  

Now, you have posed to me that one of the ways you can help these spirit children is by bringing them down to this Earth and giving them physical bodies (via copulation).  I will not contend the point that, according to the Plan of Salvation as presented by the LDS church, each spirit child of God needs a physical body, nor will I contend the veracity of this doctrine.  For the sake of the argument, I will assume that the Plan of Salvation is true and therefore each spirit does need a body (except the 1/3 who were cast out).  But, the question I will now ask you is this: Why do you need to be the one who will provide a body for those spirits?  That is, why does it have to be your own biological child?  There are so many spirit children of your Heavenly Father who are here on this Earth who already have a physical body (so that part of their progression back to God is complete) but who do not have homes or parents.  Our orphanages have so many children in them, children who need a loving mother and father.  If you really, truly cared about all of Heavenly Father's spirit children, then why do you not care about these children?  Will you turn your face away from them, pretending that they do not exist and that you have no place in helping them, in providing a loving, caring home for them?  If you have your own biological children, then you need not concern yourself with the welfare of those who are parentless?  These seems more stoic and unfeeling than altruistic, as you have presented yourself to be.  

So, here, finally, is my rebuttal to your argument.  You are straight.  You can marry the person you love and copulate with them.  You can have your own biological children.  If that's really what you want, I honestly have no problem with that in the slightest.  But, I am gay.  If I marry a person with whom I can copulate, then it will be someone to whom I am not sexually attracted, and therefore I believe my marriage to that person (woman) will be less than what a marriage should be.  Why not let me marry the man that I love and let the two of us (as husbands) adopt one or more of these children who are in an orphanage, children who already have a physical body but need a loving home in which to be nurtured, so they can have a bright future?  If you really, truly cared about all of God's spirit children, would you not want to provide more ways of allowing loving parents to adopt, rather than trying to limit the possibilities?  Do you really want to increase the number of children in orphanages?  Or do you want to decrease that number?  Do you disagree with me that allowing gay couples to adopt would help decrease this burden that our world has in orphanages?  This is my rebuttal.  And, I really do want honest answers to any and all of the questions I have asked in this post.