Almost every government position from notary to judge to attorney - general and President
confers legal privileges and rights when acting in an official capacity, and no one has ever claimed that these rights, limited to the duration for which one holds the office and as acting in an official capacity while doing so, amounts to a title of nobility.
Not exact matches
One Christian response is to say simply that the State can define marriage as it will, can
confer whatever
legal privileges on whatever couples it should single out for its protection, but that this has no bearing on the reality, which is a matter of metaphysics, not convention.