Excerpts taken from http://carm.org/god-of-old-testament-a-monster

Far from being innocent, the objects of God’s judgments were involved in gross sin and committed acts of great barbarism, such as ritualistically burning their own children to death as offerings to their false gods. Amazingly, instead of immediately destroying the people involved in such things, the actual opposite is found: the Scripture conveys that God had incredible patience and waited until the full measure of their deeds were completed. For example, while speaking to Abraham about the future exodus of Israel from Egypt, God says the following about the Amorite people: "Then in the fourth generation they will return here, for the iniquity of the Amorite is not yet complete,” (Gen 15:15).

One has to ask if mankind today would be as long-suffering with such horrible acts? Were such acts as those chronicled in the Old Testament catapulted into the twenty-first century and globally broadcast via CNN, there would no doubt be a universal outcry with military action being prescribed if such actions were not immediately halted. Why then do God’s critics feel justified in labeling the Creator as morally unjust even when God waited, in some cases, for centuries to punish the peoples involved?

After carefully examining the chief Old Testament examples that atheists use to label God as unjust, it has been demonstrated that their criticisms and characterizations are unfounded, and their understanding of the various situations flawed. Further, rather than living up to Dawkin’s caricature of being a vindictive, impatient, quick-tempered, and bloodthirsty deity, the image of God that instead emerges from the Old Testament after a thorough study is just the opposite; God is portrayed as forgiving, patient, and slow to bring forth judgment. However, He is also revealed to be a holy, just, and righteous God who will bring justice about in His time. In short, the God of the Old Testament matches the God of the New Testament.