The problem of redemption
How can an all knowing God create and then destroy? Well, how could he do it with the flood of Noah? God did indeed find an solution with Noah and his family, and you could say that people at that time experienced angels, fallens ones though, but here mankind was also destroyed because of polution to the genes of man, due to that the sons of God visited women on earth, and an offspring was produced from it. But why is the situation any different from that of lucifers fall? Could God not have come up with a solution there too? Well, I believe the inpact of the evil was greater that at the time of Noah.
It is hard to guess as to how many people there lived on earth at that time, and we are to remember that 1/3 of all the angels in the rebellion with lucifer was a much more serious in number and in what it did to the people and the earth than in Noahs days. The angels that sinned at that time of Noah, God put in prison unto the day of judgement, but I believe that has to do with that man is created in Gods image, and that is much more serious sin.
Romans 11.33 says:
Romans 11:33 33 O the depth of the riches both of the wisdom and knowledge of God! how unsearchable are his judgments, and his ways past finding out!
There is just somethings that are too hard for man to understand, but we see it all the effect of what he does.
We see the judgement in 2 Peter 3.5-7.
"For this they willingly are ignorant of, that by the word of God the heavens were of old, and the earth standing out of the water and in the water: Whereby the world that then was, being overflowed with water, perished: But the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire against the day of judgment and perdition of ungodly men." (2 Pet 3:5-7 KJV)
I will not make a comment on this myself, but let Christian Geology make some points.
Point #1: Compare the phrase "the heavens and earth, which are now" to the phrase the "heavens were of old":
When Noah's flood happened did it change anything in the upper heavens (above Earth's atmosphere)? Were there changes made to the sun, moon, or stars? The answer is NO. The heavens that were already ordained and up in the sky during Adam's day are the very same heavens that were there for Noah and his sons after the flood. And those same heavens are still there today. FACT: The flood had no effect on the heavens. All flood effects were confined to the Earth's surface and atmosphere.
Again, note the contrasting comparison between the phrases the "heavens were of old" (before the waters) and the "heavens and earth which are now" (after the waters). If Noah's flood did not alter the heavens, why does the passage clearly speak of former heavens "of old" and different heavens afterwards. This can not be an accurate reference to Noah's flood, but it could be a reference to a reconstruction of all things; a reconstruction that happened during the seven days.
The greater glory, the greater responsibility, that is what I believe is the answer as to why He could destroy it all. I believe the pre-adamite world had greater glory, as lucifer is described to be fellowshipping people on earth, so they had en greater incounter with God and angels I believe.
Isaiah 14.12-17 describes lucifer as having to do with people on earth in his destroying act
In Ezekiel 28 he is described as to have had musical abilities and used these abilities in his sancturies which he destroyed or the people therein.
Hebrews talks also about having tasted the glory of God and having an responsibility because of it.
Hebrews 6:4-6 4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, 5 And have tasted the good word of God, and the powers of the world to come, 6 If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
So there is really no problem about redemption at all.