Let’s face the fact that being a homosexual is a disease of the mind.
Despite the real fact that this has been disproven by science already, let's accept your premise and see where you take us.
Not unlike a rapist, murderer,
Neither one of these are mental diseases. Rapists do what they do to express dominance. Murderers do what they do because they believe it's the only way to get a desired outcome. It might be out of anger (heat of the moment, thus, if I understand the term correctly, actually manslaughter), or revenge (generally planned out). However it's not a disease. Murderers generally (unless they're serial killers) don't kill over and over again.
child molester, or necrophilia.
Closer. Both situations have individuals who are sexually attracted to individuals who cannot give consent. Children because they don't have the understanding of what sexual contact actually is, and dead bodies because, well, they're dead.
These are all illnesses of the mind.
As I've pointed out, no, they're not all diseases of the mind. As for homosexuality, again, it's been proven to be genetic, and actually quite normal for sexual animals to have a portion of their population engage in homosexual activity.