Kerry's status as an American citizen does not absolve him of this duty as a Catholic.
Who would find it such? I am merely suggesting that you have a justification for those values that you are ready to defend. I would hope that you could also present a justification that any thinking person, Catholic or not, could find persuasive. However, it is sufficient for me that people share my most basic values, even their justifications are not persuasive.
Kerry's status as an American citizen does not absolve him of this duty as a Catholic.
It would seem that if he claims to be a Catholic, then he ought to act like one.