Now to the heart of the letter. There were multiple battle grounds for the early Church. The church fought persecution from the Roman Empire; the early church fought slander and malice from proponents of other religions; the church had to fight to keep its story straight and its theology in line with what Jesus actually taught and the Apostles actually passed down. There were many other philosophical ideas that fought against Christian orthodoxy. Chapter 2 is a argument against "false prophets". In condemning the false prophets the author resorts to some interesting examples. It is noted that angels were not spared when they rebelled; the ancient world, in Noah's time, was not spared; Sodom and Gomorrah were not spared; and the few that were spared were those who managed to hang on and be faithful. The author then compares the false prophets to Balaam (from Numbers).
The issues here were pretty common and 2 Peter alludes to a few of them. It was being taught that because Grace covers all sin we are free to do what we want and to sin with impunity. This argument was leveled against St. Paul as well. It was being taught that Jesus never really came in the flesh (he only appeared to be a human being). It was being taught that Jesus was not really the Son of God and that his powers were only temporary. As is true in any era a certain percentage of people are led astray by novelty, by ideas that sound "more interesting" and by things that tickle the ears and the imagination. We are no different. Keeping our hearts and minds on Christian orthodoxy (while listening to the voices on the edges and those who are pushing the boundaries) is a great, but important challenge in our world today.
The warning for beginning the journey and turning back or turning to something else is pretty harsh. The author says "For it would have been better for them never to have known the way of righteousness than, after knowing it, to turn back form the holy commandment that was passed down to them (21)."