Christ's Assessment of the Church at Pergamos

The Lord commended the church at Pergamos for their works in spite of the terrible oppositions they must have faced with Satan working powerfully in the authorities that lived in this same city. But as bad as that was there was trouble 'within.' Some of their own congregation were fornicators and idolators, and some preferred to Christ's rule Nicolaitanism. And to add insult to injury the church, instead of being proactive against error within, they tolerated it. What was the church to do? What should any church do that might be like the church at Pergamos? Repent!