People were horrified at the sin they saw. They cried out to God. Notice, though, He checked it out for Himself before He acted. God hears our prayers of outrage. He also has infinite perspective, which we do not.

Genesis 18:20-21 

Then the Lord said, “Because the outcry against Sodom and Gomorrah is great and their sin is very grave, I will go down to see whether they have done altogether according to the outcry that has come to me. And if not, I will know.” -Bible Gateway link: Genesis 18:20-21 ESV