I feel the need to say a few things here.
First of all, since when is it a necessity that people are married before they can adopt?
I mean, if the entire argument FOR gay marriages is simply so they can adopt children, well, what was stopping them from adopting BEFORE they got married? If that is the problem, then, the question should be as to whether or not gays can adopt and NOT about gay marriages, seeing as how the two are not mutually inclusive. (Single people can adopt)
Also, if gays were allowed to marry, then, what is stopping them from demanding that they can marry in Christian churches? Now THAT is entirely WRONG seeing as how it is completely against Christianity anyway. If, perhaps, they were allowed to marry outside of Christianity (in a courthouse or in some other religion which believes gay marriage is okay), then that is a different story but they should NEVER take place in a Christian church. Anyone who thinks they should IS being selfish!
Also, what is the difference between a civil union and a marriage save the religious aspect? If all these gay couples are wanting is the tax savings/etc, then maybe change some laws so civil unions have all the same tax savings/etc as marriages and just have them with civil unions.
Otherwise, a marriage is supposed to be consecrated by God, which a gay marriage would not be. (at least not in the Christian religion)