If properly interpreted, you don't have to. The 9th simply tells the fedgov that, just because a right is not enumerated in the first eight amendments, that does not mean that the fedgov can therefore eliminate any or all other rights - because if the 9th is properly read with the 10th, that is the realm of the states or the people.
However, with the passage of the 14th amendment, trying to use the 9th generally creates a circular argument that did not exist prior to the 14th, and your point becomes more relevant.
Some conservatives are enamored of the 9'th Amendment because they see it as a way of restricting government, but truthfully it can be just as easily used the other way, to impose values that conservatives might find objectionable. Ponder this one - suppose SCOTUS were to declare tomorrow that gay marriage was a 9'th Amendment right, that applied to the states via the 14'th. How do you object to that? How do you show that it's somehow not a right?
No, the 9'th Amendment is best left dead - it's just too dangerous to actually use. It's no accident that there's approximately one Supreme Court case in all of American history that cites the 9'th Amendment, and that was in concurrence, and is not binding precedent.
Not so. The "privileges and immunities" clause is present in the original Constitution (Article IV, section 2, "The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States.)
I do not share the widespread view that XIV "incorporates" I-X against the States, in fact, I think that view makes no sense.