But [keep in mind that] if God did not spare the messengers that transgressed, but consigned them to hell, to the darkness of the pits, to be held there until the judgement; [and further] if He had not held back from [judging] the ancient world [then] but kept watch over Noah, one of the surviving eight, as a herald of [what] righteousness [involves], when the flood was unleashed upon the unrighteous of the world; also when the cities of Sodom and Gomorrah were completely overthrown and condemned to ashes, having [already] established powerful warnings to those intent upon an impious "in yer face" defiance. And [you know how the story goes] how He delivered Lot, whose integrity was worn down by the lawless, degraded conduct he confronted. And Lot He [indeed] delivered, after his integrity was worn down by the lawless and degraded conduct he had to see and hear, day in and day out, suffering deep torment from their recklessness with the integrity of his own life. For the Lord indeed knows how to deliver a man of reverence from out of his trials, even as He has reserved a day to deliver judgement upon the unjust.
Peter continues his warning. This is not simply a matter of whether the readers like the story. This is the stuff of life and death, just as it always has been and just as it was for Jesus when He ministered to those He served. Jesus had made it perfectly clear to His disciples that He expected a decisive awareness of the evil that is in the world that is fomented by the agents of God's enemy who are ever willing to capture the innocent unawares.
So Peter, forever chastened in the knowledge of God's makes his appeal to his readers. He not only knew about divine forgiveness but also healing. Yes, he had denied his Lord so shamefully, but then after Jesus' resurrection he was personally restored by a Friend who wasn't going to allow Peter's confusion and embarrassment to cause Him to renege on His choice that this man be shepherd to His flock. So now Peter reminds his readers of the way God's judgement has always worked itself out, as God Himself continued to work out and fulfill His promises, His covenantal blessings, with Noah, with Abraham.
And those who were honoured with hearing God's merciful message, Peter says, have also repeatedly merited God's judgement and anger. His own messengers (angels) have rebelled and it is almost too much to even think about that [he has already broached this in his first letter I Peter 4:17-18]. But Peter writes as one who has been given divine authorisation to see what was going on when God undertook His redemptive work in making the farmer, floating zoo-keeper-cum-viticulturalist, a herald of righteousness, a new Adam as it were, with whom He would "start again" after the flood. Judgement has come, meeting the depravity of what had emerged of human civilisation with a cataclysmic flood, but the end was not yet.
This active process of "starting again" can also be seen in the way Lot, Abraham's nephew, was rescued from the trials that had worn him down in a lawless and thoroughly degraded place. Without the Lord God's forbearance in preserving his life, Lot's hope that righteousness would prevail would have been at best a frightened whistling in the dark. If all he had was some cleverly elaborated myth (2:1) of his uncle's to keep hope alive then indeed Lot had no hope. But, says Peter, Lot was delivered, God keeps His promises. Even in this case, the rescue of Abraham's tormented nephew, we see how God was busy keeping His promise to one family among all the families of the earth:
… and through you [Abram] all peoples of the earth will find blessing upon themselves (Genesis 12:3)
This is the true basis for hope. God in Christ Jesus renders a new people righteous; those who resist His discipline and persist in their unjust ways had better watch out! Ample warning has been given.