The clear implication is that if you fail to perfectly apply your faith to all situations, then you probably need to support same-sex marriage to be consistent. To support their point, they cite evidence that some Christians provide services to weddings where the newlyweds are clearly engaged in sinful behavior and not sufficiently respectful of the Biblical institution of marriage. They have a point, to a certain extent. We Christians should seek to avoid sin in all its forms, rather than arbitrarily deciding when to be offended by it.

But they lose their grip on that point by conflating a pure institution (male-female marriage) that may nonetheless be corrupted by sinful people, with a Biblically impure institution (same-sex marriage) that is sinful by definition. For obvious reasons, Powers and Merritt would rather the discussion be about sinners and saints than about right and wrong: it’s easier to marginalize a sinner than it is to wave away sin.

But there is a reason so many faithful Christians, in spite of their sins, are so protective of the God-given institution of marriage. Biblical marriage is a sanctifying institution, which is one reason why many Christian denominations treat marriage as a sacrament on par with communion and baptism, both of which are freely denied by the Church when it is clear that its potential participants (or their guardians) have no interest in the underlying reason or importance of the sacraments.