It seems that some of the false teachers described by Peter had been accepted as members of the church, and in fellowship with other believers.  Having analysed their behaviour and motives in this chapter, he now makes one of the 350+ apostolic conditional statements starting with "if".  These are an especially important part of Biblical theology because they stimulate us to think clearly about holy things (2 Peter 3:1).  The "if" statements give us the consequences of possible actions, and therefore stir our hearts to flee from all that will bring God's curse but embrace what leads to His pleasure and blessing.
 
The false teachers of this chapter had once been impressed with the true gospel, and had come to know Jesus Christ and had learned to walk His way; so their defection from the truth, dragging others with them, was a very serious matter indeed.  Their ungodly lifestyles and flagrant disregard of the apostles' teaching had marked them out for judgement.  Peter says that their apostasy had left them in a worse situation with God than when they were ignorant of the truth (Hebrews 6:4-6).  Hard words indeed! But as every former backslider knows, it is only when they understood the gravity of their rebellion before God, that they wanted to repent and come back home (Luke 15:17-20).
 
It is every pastor's nightmare to see a believer reject the gospel.  Worse still is a leader who is unrepentant of error, or teaching a different gospel (Galatians 1:8-9).  Alas the church worldwide is still confronted by such spiritual wreckage. What is to be done?  Jesus was very stern about the dangers of flouting God's powerful grace which has overcome the Evil One (Matthew 12:43-45), and Peter is uncompromisingly graphic in saying "A dog returns to its vomit".  

Despite the liberal ideas that keep infiltrating the church, applauded by those who choose to tear pages out of the Bible in order to be socially acceptable (2 Timothy 4:3-4), the Bible offers no comfort to any believer (teacher or learner) who continues to repudiate the truth and willingly welcomes evil.  The message to the church is simple: ‘Don't go there, don't even think about it’!  To the sinful leader, the only message is, "Repent"!  In days when the worldwide church faces challenges from heresy, error, compromise, syncretism and persecution - we need the message of this chapter more than ever, to help us stay on track with Jesus.