The Wickedness done via sexual immorality (the act of misusing, and perverting sex), influences humans to behave in a negative way towards each other.

Genesis 6:1-2 (NKJV)

1 Now it came to pass, when men began to multiply on the face of the earth, and daughters were born to them, 

² that the sons of God saw the daughters of men, that they were beautiful; and they took wives for themselves of all whom they chose.

The intentions, thoughts and imaginations of human beings can be affected negatively and corrupted in regions where immoral sexual behaviors like;

rape, homosexuality, bestiality, women trafficking, prostitution is taking place.

Genesis 6:5-6 (NKJV)

⁵ Then the Lord saw that the wickedness of man was great in the earth, and that every intent of the thoughts of his heart was only evil continually. 

⁶ And the Lord was sorry that He had made man on the earth, and He was grieved in His heart.

Genesis 6:11-13 (NKJV)

¹¹ The earth also was corrupt before God, and the earth was filled with violence. 

¹² So God looked upon the earth, and indeed it was corrupt; for all flesh had corrupted their way on the earth.

The Ark Prepared

¹³ And God said to Noah, “The end of all flesh has come before Me, for the earth is filled with violence through them; and behold, I will destroy them with the earth.