Revelation 2:6

‘But this you do have, you hate the works of the Nicolaitans which I also hate.'

We know little about the Nicolaitans but they were clearly influential then in leading astray the churches, and were probably followers of a Nicolaus (variously identified). They apparently taught that it was good to eat things sacrificed to idols and to behave immorally, engaging in self-expression and full release (see Revelation 2:14). This meant both a compromise with the Roman religion, with its sacrifices to Roma and its love feasts, and with other religions, thus denying the exclusivity of Christ. This then meant involvement in idolatry and licentiousness.

To openly eat things sacrificed to idols would be seen as acknowledging the gods who were being ‘worshipped', and licentious behaviour, introducing overt sexual expression outside marriage (often with ‘sacred prostitutes'), was a common feature in many religions of the day. Misused sex and idolatry, two constant enemies of the church, these things Christ hates. But there was none of this in the Ephesian church. They had maintained their purity.