Has God Overreacted To The Sins of Humans?

Atheists often claim that the existence of evil proves that, if God does exist, he can't be both omnibenevolent (all-good) and omnipotent (all-powerful). Formally, the argument looks like this: (1) If God were all good, he would want to get rid of evil, and, if God were all powerful, he would be able to; (2) evil exists; (3) therefore, either God can't get rid of evil or he doesn't want to. This is simply called "the problem of evil argument."
The problem of superfluous evil

Survivors of the 2012 Japanese earthquake/tsunami (source)

Other more thoughtful atheists, however, have recognized that some good can conceivably come from God's allowing of some evil. It is not hard to imagine, for instance, that a person's experience of pain and suffering could have a maturing or purifying effect for which they are later thankful. Most people can probably think of at least one painful memory for which they have come to be thankful, due to the good that came from it. For this group, evil per se is not the problem. They modify the problem of evil argument into something called the "superfluous evil argument." The problem, in this case, is not the existence of evil itself but the sheer amount of it--that is, much of the evil is completely superfluous (or unnecessary). These non-theists claim that the punishment doesn't fit the crime. Hasn't God overreacted to the sins of humans? [1]
This is a legitimate question that deserves a Christian response. Think about it from the atheists' perspective--curious Adam and Eve ate the beautiful fruit from forbidden tree that God created and, as a consequence of their disobedience, humanity has since dealt with hurricanes, tornadoes, earthquakes, famines, pestilence, murder, war, abuse, rape, genocide, death, etc... On its face, this punishment seems out of proportion to the crime committed. In the end, the conclusion is the same as that of the first group: if God exists, he can't be all-good and all-powerful. If anything, God is a cosmic sadist, like a little kid who burns ants in the sun with a magnifying glass.
Moral and Natural Evil

The Great San Francisco earthquake of 1906

When surveying the above list of the consequences of sin, one thing becomes almost immediately obvious; there are two different types of evil there. Hurricanes, tornadoes, and earthquakes are qualitatively different from abuse, rape, and genocide. The first set naturally occurs and, therefore, is called "natural evil;" whereas, the second set is related to the moral decisions of human beings and is, therefore, called "moral evil." The existence of moral evil is easy enough to explain--it is humanity's own fault. It is not clear that God should be on the hook for willful human actions. [2] What does seem superfluous, however, is the natural evil. There is a reason we call them "acts of God" in our insurance policies; they are not human actions. In 1906, the Great San Francisco earthquake struck, killing somewhere between 1,000 and 3,000 people. In 1931, more than 1 million Chinese were killed  by extreme flooding. In 2005, Hurricane Katrina ravaged New Orleans, taking the lives of more than 1,800 people. On December 26, 2004, a tsunami came ashore from the Indian Ocean and killed approximately 250,000 people. In 2010, a 7.0 magnitude earthquake killed 300,000+ Haitians. Think also of the Great Dust Bowl, the bubonic plague, the volcanic destruction of Pompeii,  etc... Why would God do this to humanity? For non-theists, this seems a bit like beating a small child in the head with a metal rod repeatedly because he carelessly spilled his milk. It quite literally is overkill.

A reasonable Christian response

There are at least two reasonable responses that the Christian can make here. First, it is not obvious that such things as earthquakes, hurricanes, and tsunamis are the result of sin. These phenomena are all part of this magnificent, organic globe that God created ex nihilo. They serve positive restorative roles for the environment. Christian theology does, in fact, teach that the natural order doesn't work like it should (Romans 8:19-21); however, we don't know precisely what has gone wrong, other than the weeds that sprang up in Adam's garden.
Secondly, while humans can't directly cause tornadoes, hurricanes, and earthquakes by the action of their own wills, moral evil can certainly accentuate the effects of natural evil. It seems that the "superfluous" natural evil, for which non-theists would blame God (if they believed he existed), may be the fault of humans after all.

Humans and natural evil

Loma Prieta earthquake, San Francisco, 1989

Compare the 1989 Loma Prieta earthquake in San Francisco (6.9 magnitude) to the 2010 Haitian Earthquake (7.0 magnitude). In San Francisco, 63 people died; in Haiti, over 300,000 died. What accounts for the vastly greater number of deaths and suffering between the two similar-magnitude earthquakes? The natural evil is the same, but the moral evil is not. The sinful, systematic corruption within the Haitian society had left the nation crumbling, with poor infrastructure, inadequate building codes, and countless slums. By contrast, San Francisco was relatively orderly, regulated, and free of corruption. (Notice that I wrote "relatively.")

Aftermath of the 2010 Haitian earthquake

I argue that the Haitian earthquake does seem superfluous while the San Francisco earthquake does not. The former does create a crisis in the belief in the existence of God; whereas, the latter does not. But, as stated above, the Haitian earthquake's superfluous nature is arguably the problem of human moral evil as much as it is the act of God.
Human moral failure makes natural evil considerably more fatal and painful than it would be otherwise. It is conceivable that such things as tectonic plate movement, tornadoes, hurricanes, and forest fires all existed before sin. However, these things were not pain- or death-inducing. They could have existed in some sort of harmony with un-fallen humanity.
The main point here is that the apparently excessive nature of natural evil is not logically sufficient to conclude that an omnibenevolent and omnipotent God can't possibly exist.

A concluding exhortation to reconciliation and restoration

What God has cursed, no human can un-curse. If entropy is part of what has gone wrong with creation (and I think it is), there is nothing we humans can do about that. We must simply wait for the day that the Lord returns and peels back the heavens for his great restoration of the whole created order. However, differentiating between moral and natural evil sets us free from a totally fatalistic eschatology (or doctrine of the end times).[3]
What the Church can work to restore is the damage caused by by the catalytic moral evil of human beings. We can work to correct despotic corruption, human oppression, failing infrastructures, and poor distribution. In short, we can carry the restorative power of the Gospel to all the nations, praying that the Holy Spirit would work to restore the moral and spiritual sensibilities of the people and pull them out of the superfluous spiral of unnecessary natural suffering. [4]

----------------------------------

[1] Logically neither of the above arguments proves that God doesn't exist. It merely attempts to prove that, if God does exist, he is nothing like the God of the Christian Scriptures. He'd be something more akin to the pantheon of ancient Greeks.
[2] This raises other questions about free will, which are too extensive to be dealt with here. I am not arguing for a completely free will (libertarian free will).
[3] For an excellent analysis of what the new creation might be like physically, check out Max Andrews' blog post on the topic here.
[4] Due to its controversial nature, I did not mention global warming (or "climate change"). However, if it is, in fact, caused by human actions, it only makes my case stronger.

---------------------------------

Christian philosopher William Lane Craig explains the two versions of the non-theist argument from the existence of evil.