http://thegospelcoalition.org/blogs/tgc/2012/07/19/gay-is-not-the-new-black/
Some highlights from a similar article he wrote
The first problem with the idea of conflating "sexual orientation" and race is the fact that homosexuality is undetectable apart from self-identification. Determining whether or not a person is black, Native American, or female usually involves no more than visual verification. However, should doubt remain, blood tests, genetics, or a quick trip up the family tree would suffice. Not so with homosexuality. There is no evidence that can confirm or deny a person's claims regarding sexual orientation.5
Moreover, the homosexual community itself has made this identification even more complicated in an effort to distance itself from those whose same-sex behavior they find undesirable. The Jerry Sandusky case is a prime example. Sandusky is accused of molesting numerous young boys during and after his tenure at Penn State. However, try placing the label "homosexual" on his activities and the backlash will be swift and unequivocal. "Pedophiles are not homosexuals!" is the consistent refrain coming from the homosexual community, media, academia, and the psychological/medical establishment.6
It should be noted that the right to marry is one of the most frequently denied rights we have. People who are already married, 12-year-olds, and people who are too closely related are just a few categories of people routinely and/or categorically denied the right to marry. Hence, the charge that it is wrong to deny any person a "fundamental right" rings hollow. There has always been, and, by necessity, will always be discrimination in marriage laws.
Third, there is a historical disconnect. As early as the time of Moses, recorded history is replete with interracial marriages. In our own history, the marriage of John Rolfe and Pocahontas in the 17th century,9 along with the fact that anti-miscegenation laws were usually limited only to the intermarrying of certain "races" of people (i.e., black and white), stands as historical evidence of the legal and logical inconsistency of such laws. Thus, unlike same-sex "marriage" advocates, those fighting for the right to intermarry in the civil rights era had history on their side.
Fourth, there is a legal disconnect. One thing that seems to escape most people in this debate is the fact that homosexuals have never been denied the right to marry. They simply haven't had the right to redefine marriage. But don't take my word for it; listen to the Iowa Supreme Court in their decision in favor of same-sex "marriage": "It is true the marriage statute does not expressly prohibit gay and lesbian persons from marrying; it does, however, require that if they marry, it must be to someone of the opposite sex."
There it is: not only in black and white, but in a legal decision. Homosexuals haven't been deprived of any right. How, then, do those on the side of same-sex marriage continue to make the claim that this is a civil rights issue? The key is in the next paragraph:
[The] right of a gay or lesbian person under the marriage statute to enter into a civil marriage only with a person of the opposite sex is no right at all. Under such a law, gay or lesbian individuals cannot simultaneously fulfill their deeply felt need for a committed personal relationship, as influenced by their sexual orientation, and gain the civil status and attendant benefits granted by the statute.