Who is correct?
First, John and Jim would not have constitutional rights for being gay. They would have constitutional rights for being U.S. citizens. At best they could argue that being gay is the reason for the infringement of a right. Granted, this is mainly just a semantic point, and the upshot still comes out close to what you said.
Second, the positive assertion of one's constitutional rights is tempered by the passive retention of another's.
And third, unless Dave is operating under authority of a government body (such as administering a state-run housing complex), then he is not capable of violating constitutional rights. He could, however, be subject to equal housing ordinances, and that might be a better battlefield for the analogy you are trying to make. But that would likely still result as favorable to Dave - see my second point - resulting in the invalidation of the equal housing law. However, if that law is written in such a way as to grant benefits (e.g. a tax break to those that are in compliance) instead of requiring adherence, then Dave may face a choice between maintaining his rights and obtaining a benefit.
Good post! The problem with asserting judicially enforcable rights under the 9th Amendment is that two claimed rights can contradict one another. Some libertarians argue that the 9th grants federal judicial enforcement power on unenumerated rights. But what happens when two claimed rights contradict one another, or when an unenumerated right conflicts with an enumerated one?
Under this reading of the 9th, an unborn baby can't have a right to life without pregnant women losing their right to abortion, and vice-versa. Blacks can't have a right to be served at a racist restaurant owner's lunch counter without the owner losing his right to choose for himself whom to serve, and vice-versa. Gays can't have a right to marry one another without the voters losing their right to decide the definition of marriage, and vice-versa.
In all the above cases, I refer to judicially enforced rights, claimed under the 9th Amendment. The court can't grant one without denying the other.
The best understanding of the 9th seems to be that it was intended to leave states (and their voters) free to recognize unenumerated rights if they so chose, and to bar the federal government, including the federal courts, from interfering with them. In other words, the Supreme Court could not deny or disparage other rights if granted.
It sounds really nice to say that we as citizens have every right we might imagine, but at many points such rights conflict. I'd prefer the legislative branch to the judicial in sorting out these rights.