Not to pick on just your post, but it was like the lkast straw. The level of misinformation and failure to understand basic civics, basic logic, basic biology and so much else in this thread is astounding. That the post quoted here even exists is embarrassing. It is ignorant of any understanding of the legal issues involved and how constitutional law works.
Conservative, there is a host of information on what equal protection is and isn't online. You might want to read some of it. I am, out of the kindness of my heart, going to help you out and show you why your argument fails legally(that it is also a logical fallacy is beside the point for purposes of this).
Marriage in the US is a basic civil right. You may not like it, but it has been ruled to be one for many years, and in many cases. The only way you can change this is with a Supreme Court ruling(since they affirmed it as a right, multiple times), or by constitutional amendment(how successful have amendments that take rights away from people been?). Neither of these is at all likely to happen in the foreseeable future. In the absence of a Supreme Court ruling or amendment making marriage not a right, trying to claim it is anything but is silly.
Now you are right, equal protection does apply to every one. Otherwise it would not be equal protection. But this leads to your ignorance. You do not understand what equal protection actually is. There are limits to all rights in this country. TO impose such a limit, there are various tests. In all the cases you mentioned, Rational Basis Review is that test. Basically, is limiting the right for that group of people serve a legitimate state interest, and is the distinction of that group arbitrary. In the case of family members, the answer to the first question is almost certainly yes, and the second no. There is a potentially good reason why allowing close relatives to marry might be a negative thing. Now, apply the same standard to same sex marriages. Is there a legitimate state interest in denying those marriages? None have been put forth so far. Quite the opposite, there are legitimate, compelling reasons to allow those marriages(2 parent stable households are best for raising children). Is the distincrion of the group arbitrary. This is a more interesting question and a case could be made either way, but probably yes. Based on the fact the state has no legitimate interest in denying those marriages, SSM bans, using the same legal standard(that is equal protection) fails, while bans on incestuous marriages don't.
So now you understand how equal protection works, and also why arguments against SSM based on incest, bestiality, pedophilia, polygamy or whatever other scenario you can image do not work. You will of course ignore everything I said here since none of it is what you want to hear, but sometimes it is good to point out how the law actually works, and not how random guy on the internets thinks it works.
