I've made this point a number of times through the years. One of the talking points of the gay rights movement is to invoke the civil rights movement, to which the other side responds (obviously) gay is not black, sexual orientation is not race. See for instance this thread on WorldMagBlog; as one commenter put it:
Comparing the struggle of gay people to what happened in the civil rights movement indicates that we can tell who is gay by their outward appearance. THE CIVIL RIGHTS MOVEMENT WAS ABOUT CLEARLY VISIBALE DIFFERENCES. I do not know what brain cramp homosexuals are suffering from that they cannot see this clear truth.
Richard Posner, certainly not a man known for suffering from "brain cramps," had a passage in Sex & Reason which well puts the issue into perspective:
[G]iven Title VII and cognate laws, is there any reason to exclude homosexuals from a protected category that already includes not only racial, religious, and ethnic groups but also women, the physically and mentally handicapped, all workers aged 40 and older, and in some cases, even young healthy male WASPS? Is there less, or less harmful, or less irrational discrimination against homosexuals than against the members of any of these other groups? The answer is no.
-- Sex and Reason, p. 323