There is a big difference between strategic waiting and apathy.  The first has a purpose in mind which cannot be completed until the time is right: the second sees no end-point, irrespective of the time.  But God is never apathetic; He cares so deeply about everybody that He does not want anybody to perish so He gives more time for sinners to repent (2 Peter 3:8-9).
 
This was not just Peter's gospel, but Paul's as well, who wrote in Romans 2:4: "Or do you show contempt for the riches of his kindness, tolerance and patience, not realising that God's kindness leads you towards repentance?"  Both Apostles taught that divine 'delay' was not God's indifference, but the result of God's kindness - and so a response was required. Failure to respond in repentance and faith was to despise God's generosity (Romans 2:4).  

But there were false teachers who resisted the Apostles' teaching and preached a very different interpretation (2 Peter 3:4).  They taught that the 'failure' of Christ to return was evidence that God had no more interest in the world or the church, and therefore there was no point in believing the Apostles (whose teaching is inspired by God in the same way as the Old Testament Scriptures).
 
The Bible is not always easy to understand.  But you should start to smell heresy when a hard bit is twisted to mean something which is inconsistent with what is plainly taught elsewhere in the Scriptures.  In Peter's day, lots of false teachers were trying to make a name for themselves (2 Peter 2:1).  If they could remove the possibility of Christ's return in judgement, they would eliminate the need for personal accountability, and therefore could more easily sway their hearers to believe what was false.  Often the most dangerous teaching does not come from secularists or atheists, but from religionists who have contempt for God's grace, and His patience in giving them time to repent.  Avoid such people like the plague; they have the evil potential to drag you away from the truth of the gospel and the saving grace of Christ (1 Timothy 6:20-21).