I basically said that good and evil have been around since the beginning, and you can clearly see that from the beginning.
If you have no idea what I'm yakking on about, quickly look here.
In my Institute class, we briefly recapped some of the events in the book of Genesis, the events that show us the good and evil that perpetuated in Adam's posterity.
Here is an example of the wickedness in Cain’s posterity:
And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,
That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.
And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.
And God looked upon the earth, and, behold, it was corrupt; for all flesh had corrupted his way upon the earth.
And God said unto Noah, The end of all flesh is come before me; for the earth is filled with violence through them; and, behold, I will destroy them with the earth. (Genesis 6)
By the way, the account in the book of Moses is slightly different. Go ahead, have a look at Moses 8:14-20.
Some translators way back got the sons and daughters mixed up.
And note: the 'sons of God' were those who made covenants with the Lord, and the 'sons of men' were those who would not make covenants, or obey their covenants, with the Lord. And where it talks about selling themselves, it means they were married out of the covenant.
What does that have to do with the story of Noah?
Perhaps we really should understand what was going on in that day - what the conditions were in the time of Noah - for us to understand just how bad it got, and why the Lord decided a flood was necessary.
Elder Joseph Fielding Smith said: “The fact was, as we see it revealed, that the daughters who had been born, evidently under the covenant, and were the daughters of the sons of God, that is to say of those who held the priesthood, were transgressing the commandment of the Lord and were marrying out of the Church. Thus they were cutting themselves off from the blessings of the priesthood contrary to the teachings of Noah and the will of God.” The people in this time were foolish. They were throwing away their covenants and promised blessings.
This is an interesting doctrine - to marry someone within the covenant, or within the Church today. The apostle Paul told the Corinthians "Be ye not unequally yoked together..."
"Perhaps Paul wanted them to see that religious differences are fundamental differences. Religious differences imply wider areas of conflict. Church loyalties and family loyalties clash. Children’s lives are often frustrated. The non-member may be equality brilliant, well trained and attractive, and he or she may have the most pleasing personality, but without a common faith, trouble lies ahead for the marriage. There are some exceptions but the rule is harsh and unhappy one. There is no bias nor prejudice in this doctrine. It is a matter of following a certain program to read a definite goal.” So what does this mean for us today?
Clearly I mean no offense for those who have married outside the Church, or who have parents or friends in that situation. But you can see the counsel is sound. There will be conflict in most cases, and there is alot more to it than a happy productive home life. There are priesthood blessings that we are each entitled too, if we make sacred covenants.
You can read the Lord’s statements about the last days in Joseph Smith Matthew 1:41-43 (a better translation of Matthew 24:36-39).
So why did the Lord flood the earth?
President John Taylor suggested that the world was so wicked that children grew up with no choice but to be wicked. At that point, when there was no chance to choose righteousness, sending innocent spirits from heaven to earth was no longer just.
“By taking away their earthly existence he prevent them from entailing their sins upon their posterity and degenerating them, and also prevented them from committing further acts of wickedness.” 
Did you know the scriptures speak of two separate times when the Lord will cleanse the earth of wickedness. One, at the time of Noah. Two, at the second coming.
And Joseph Smith Matthew tells us how those two time periods will be like each other. The biggest difference is that the earth was cleansed by water in the days of Noah, and at the Second Coming it will be cleansed by fire. These two events are a type of how we are cleansed by the baptism of water and the baptism of fire – the cleansing of the soul that occurs when we truly receive the gift of the Holy Ghost.
It makes you think of what preparation we may need, and how we can not be like the people in Noah's time. Did you see the people in the painting above? People mocking the prophet, laughing at his warnings, ignoring them or just not taking them seriously. How could it possible rain and rain and rain to flood the earth? Think of the warnings and counsel we have received over the years from our modern-day Noah's.
An example of the preparation required was once spoken of by Elder Ezra Taft Benson:
“The revelation to store food may be as essential to our temporal salvation today as boarding the ark was to the people in the days of Noah.” 
Preparation will be necessary for us to endure times of tribulation.
If we may preserve our physical lives by following the counsel of the prophets, how much more important is it to save ourselves from spiritual death by following the counsel of the prophets?
 Old Testament Student Manual, 4-8, bold added
 Spencer W. Kimball, The Miracle of Forgiveness, p. 238
 John Taylor, in Journal of Discourses, 19:158-59
 In Conference Report, Oct. 1973, p.91