At the heart of the divisions which have beset the Anglican Communion since 2002 is a profound disagreement over sexual ethics, in particular whether same sex unions can be blessed by God in the light of the teaching of the Bible. The teaching of GAFCON is that the Bible is clear on three vital points.
First, that sexual intimacy outside of heterosexual marriage is forbidden by God and not in the best interests of humans.
Second, that persistent behaviour of this sort puts those who engage in it outside the kingdom of God and therefore at risk of losing salvation.
Third, acceptance of this behaviour in the church means that the full gospel cannot be preached, since the full gospel requires repentance from sexual sin.
But there is more to it than that. The Bible tells us that in a society in which the truth about God is supressed, the consequence is godless sexual licence. This is a sign of an unhealthy community in deep trouble.