@mysteryman,
It was inevitable that you would bring this up, and i suspected that you would. Are you, then, alleging that people only possess those rights which are specifically granted to them by the constitution? Even the constitution itself does not agree with that. The ninth amendment to the constitution reads, in its entirety: "The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people."
However, let me play your witless game: if as you say no right exists to discuss matters not on the agenda of a meeting, then you should be able to point to it in the Constitution, OR any federal court case that has been decided.
So, since you say no such right exists, prove it.