One of the most salient teachings of Jesus - and one of the very hardest to follow - is 'Judge not, lest ye be judged'. I see this as the expression of a core spiritual truth; that if we live as ones who are forgiven, not from merit but from grace, that we are enabled to share that mercy and forgiveness and grace with others. It is about the divine love overflowing through us. To judge - and I take that in the sense of 'to condemn' - is to separate ourselves out from that overflowing grace and thereby to invoke a solemn judgement upon ourselves. "The measure that you give will be the measure that you receive"; "Forgive us our sins as we forgive those who sin against us" - these are expressions of the same core spiritual law. I do sometimes wonder whether this is the only thing that needs to be known and lived in order to be a Christian.
However, for my purposes in this sequence, the conclusion that I draw is that if a Christian brother or sister has prayed through a situation and come to a particular discernment then it is not for any other Christian to stand in judgement and condemnation over them. To start denouncing a fellow Christian as a sinner is a) to state the obvious, but b) more importantly, to demonstrate a failure to understand the gospel, and thus, to exclude oneself from the Kingdom.
This is not to say that all discrimination is abandoned, that 'anything goes' - it is simply to affirm the profound spiritual respect which we are called to offer one another as fellow baptised Christians. We are all sinners, and we do not get to heaven through our own merit. Possibly a divergence of view will lead to a failure of shared communion - 'let them be to you as a gentile and a tax collector' and so on - but that can be done in a Christian spirit or in a judgemental spirit. Only one of those is Holy.
So this is absolutely key to the discussion about marriage. That is, if we are to truly and mutually discern what is God's will for our community today, we need to be able to listen with holy ears to things that might otherwise shock us. I do not believe we need to be afraid of this.