So I wrote up a long answer, but my train of thought was difficult to follow, and I was addressing a lot of things at once, so I'll just try and break things down and get more information. I don't know much about U.S. history. When those laws came into place, was it popular opinion that black people were being discriminated against? On some level people just know when somebody is being hard done by. In the case of the Classical Liberal theory thing you were talking about, the analogy works because people know it's unfair. You seem to be implying that the law changed the way people feel, but I would say it's the other way around. Also, in order for a gay person to be discriminated against on the level you were illustrating would require a huge cultural and political shift which I simply don't see happening. My original post wasn't the "general case", it was making the assumption that we are living in today's society and with no major reversals of social progress.