Actually, the government does not grant rights. Rights are inherently reserved by the people. See Amendments IX and X. Unfortunately for same-sex marriage advocates, Supreme Court case law on the "right to marry as a natural right is linked with procreation, child-rearing, and the traditional family structure. I am not up on current case law, but reinterpretation is certainly possible.
This argument doesn’t hold much weight. Complexity in lawmaking has never been an obstacle before. The US Tax Code contains 2.8 million words and 6000 pages of text. If there’s any revenue to be gained, it will find it’s way into the tax code. There is an entire industry of legal professionals devoted to understanding and interpreting the most convulted regulations our lawmakers can devise.
Wrong again. Let’s ignore for a moment the recent statutes which prohibit same-sex marriage, of which there are many. There certainly are statutes which specifically relate and refer to the male-female relationship. You can view Marriage Laws for all 50 States, DC, Puerto Rico at the Cornell Law website. Although not all states maintain complete online database, in a few short minutes you should be able find various examples, particularly related to rights and responsibilities involving property. You may find the term “feme sole” particularly interesting. Should we dismiss the idea of recognizing same-sex marriages because changing these existing laws would be too difficult and time-consuming?
I tend to disagree. There certainly is a great deal of intolerance out there. That’s undeniable. However, open homosexual partnerships have gained a great deal of acceptance, judging by our popular culture. I believe the reason why homosexual marriage has not been recognized is more benign. There is a natural tendencey not to alter the status quo, at least not suddenly. New, liberal ideas have a natural progression. When the more militant members of the pro-homosexual marriage movement attempt to force their way through the legal system, there’s a reactionary movement against it. With the spate of marriage definition clauses, that should be obvious. These tactics hit at people’s comfort zones. Rather than widespread bigotry, I think the general atttiude is that recognition is unnecessary. While some people may not like the idea, or find the concept repugnant, or contrary to religious principles, acceptance of these relationships will probably come with time and patience. (perhaps a long time). What is needed are logical, affirmative reasons for average people to accept these relationships as equivalent to the traditional male-female marriage.
I don’t follow. How does legally recognizing same-sex marriages reduce prejudice? As far as I know, no law can change what’s in a person’s mind.
No more fundamental or complex than the changes required to recognize same-sex marriages. In the case of polygamy involving one man and multiple women, I would argue that the legal changes would be less complex. But again, complexity has never been a legal barrier before. That’s one of the reasons why we have lawyers 
Not yet. Got any other reasons?