The point is that the bride has committed no sin. All she has done is to "declare" that she supports same sex marriage. We are not told what her motive is for that. It is obvious that she is about to marry her fiance who is a man, so she is not intending to engage in same-sex marriage herself. Just because we declare our support for something doesn't mean that we intend to engage in it ourselves. It may be that we might be defending people from hateful bullies who prey on vulnerable people. The reality it, same sex marriages are part of our society now and there is little we can do about it. A person's sexuality is none of my business.
At present, the Presbyterian Church of New Zealand does not support same sex marriages, and there is a situation arising where ministers could be subject to complaint under the Bill of Rights if they decide not to agree to marry such couples. This is a conflict between the law of the land and the principles of Christian holiness. It is now a condition for secular marriage celebrants to conduct same sex marriages as part of their contract, otherwise they cannot be appointed as celebrants. So a Presbyterian minister has to make a decision whether to comply with the Bill of Rights and not discriminate between a standard marriage and a same-sex marriage, or face legal action against him for refusing to marry same-sex couples.
I need to make it clear that as a Christian believer, I don't support same-sex marriages, and if I ever considered being a marriage celebrant, I would refuse the role if I was required to conduct such marriages. But I don't support the bullying of those who show their support for it, as if they have committed some grievous sin by declaring their support. There are many worse sins that are rampant in our church congregations being swept under the carpet than just mere support for something many church ministers disagree with. I think the present situation with this bride is majoring in a minor, when that minister should be dealing with other more grievous sins in his own congregation. It goes along with Jesus' comment about taking the log out of one's own eye before trying to take a speck out of another's.