One of the key theological insights that I hang on to, which came to me from Bonhoeffer (articulating the Lutheran tradition) is 'Pecca Fortiter' - 'sin boldly'. There is, I think, a right way to understand this, and a wrong.
The wrong is the one that Bonhoeffer chastises in 'Cost of Discipleship', which is 'cheap grace'. This way of understanding the phrase effectively means - do what you like because you're covered by grace anyway. It becomes an antinomianism only half a breath removed from a complete licentiousness. One of my favourite quotations of Wittgenstein: 'If what we do now makes no difference in the end, then all the seriousness of life is done away with.' What we do matters in the long run and this way of understanding the action of grace seems to me to do away with all sense of better and worse, all that speaks to us of quality, or excellence, or holiness.
In contrast to this I would argue for a way of understanding 'pecca fortiter' which is centred upon relieving us of our burden of guilt and sense of failure. It is true that we cannot earn our way to heaven; it is also true that everything that we do is going to be tainted by our sin and failures. What this phrase means in this context is that we should not let the fear of failure prevent us from seeking to grow in faith. Of course, what we do might be a fearsome failure, a spectacular example of what not to do - but there is no place where we can go that will take us away from the love of God revealed in Christ. So long as we are constantly seeking him, constantly seeking to grow closer to him, then we can trust that he will hold on to us and no matter what sort of mess we find ourselves in, he will be able to pull us out of it. So I take 'pecca fortiter' to be a realistic maxim of encouragement. We have the authority to judge the angels, yet we will not be able to exercise such judgement unless we have grown in maturity ourselves. It is through being set free from the fear of failure that we will learn and develop that capacity for judgement. We are rather like toddlers learning to walk - we have to try and fail many, many times before we can start making strides.
In other words, if a group of Christians, after a great deal of prayer and reflection, come to the conclusion that a radical change in behaviour is led by the Spirit - then a fear of the consequences (or a reference to keeping the rules) is not enough to say that it is wrong. That group of Christians themselves have the authority and the right to test that particular spirit and to see if the changes tend towards holiness and righteousness or otherwise. This, after all, is what happened in the first-century debates about circumcision and kosher food laws. I think the same applies to our struggles over sexuality today. Put simply, we need to trust the baptism of our brothers and sisters.