I think Kim Davis would be the first to disagree with that statement. It was precisely her Christian faith that gave her the conviction to oppose the same-sex marriage, and anyone who says otherwise does her a disservice.
Probably so, but the fact of the matter is that it did not require her to be a Christian in order to understand the nature of marriage.
I think that is what one gets when one reads a little bit of context into the extract:
It is not because of her religious faith that Davis understands the nature of marriage. Non-Christians, too, have always understood (until the mania of the past few years) that marriage is a union of man and woman. That understanding was firmly in place long before the time of Christ.