Our Bill of Rights AND Constitution draw that line. Too bad our constitution is no longer controlled by the congress but rather regulated by the courts.
Also, the Ninth Amendment deals with indentured servitudes - not gays.
The best part about the Ninth is that the Ninth only includes amendments 1-8....
An Amendment cannot pertain directly to a future Amendment.
There are procedures to deal with issues such as this as (usually) addendums or repeals.