Genocide to the cities and earth cause they were FULLY corrupt. Letting it strive would produce nothing good and and only bad. But man is not allowed to make the same judgment and punishment like God.
Those cities never existed this is only mythology, but I just showed you how this biblical "God" would treat people not having "decent sexual tendencies" (according to the Bible)
The babies were killed to disprove the Egyptian gods.
Oh yeah I know that, but first despite the fact that never occured (I hope you do not believe in Santa Claus either), such idea of killing babies who are the most innocent beings was something that we could not really consider as a "respectable" action. And I prefer go to hell with decent people not believing in such god than going to heaven with people believing in him and doing terrible things.