Below is my 1,200 word summary of a lengthy treatment of 'the anger of God' by Lactantius (a late 3rd - early 4th century Christian). My posting this is not an endorsement of all his words, but simply a way of making ancient Christian writings more accessible to contemporary Christians.
THE ANGER OF GOD (Lactantius)
To Donatus, in regards to the anger of God, that you might know how to refute those who represent God as being without emotions…
Many believe that God doesn’t get angry. Some believe this because God is ‘good’. Others believe this because God is ‘indifferent’. But both such beliefs are great errors that must be refuted. My refutation comes not from my own intellect (human intellect is actually the source of the errors!), but from the revelation of God. After all, even the greatest philosophers have admitted that, without God, human wisdom is found in recognizing that we know nothing.
To find the truth of the matter, we must abandon polytheism in favor of the one true God and recognize Jesus as the primary source of revelation. In doing so, we can discern which of the following is true: Either God has anger but not kindness, neither kindness nor anger, kindness but not anger, or God has both kindness and anger.
As for option 1 (God has anger, but not kindness), no one has ever said such a thing (for it is absurd). Just looking at the world, we recognize that it is filled both good and evil. If God is only angry (and thus the source of evil), then how did good come into the world? Wouldn’t the source of the good better be called God? So it is clear that this option is deeply flawed.
What about option 2 (that God is indifferent, having neither kindness nor anger)? This is the view of the Epicureans. But what sort of God is never moved? What sort of God is un-involved? How is an indifferent god any different from the god of the atheists? Epicurus backed himself into a terrible corner. The most that can be said for this view is that it is consistent.
What of option 3 (that God has kindness, but not anger)? This is the view of the Stoics. They argue that anger is a negative emotion and, thus, beneath God’s goodness. We come, here, closer to the truth of the matter than the previous options (for it is certain that God is kind). Yet we still fail. For they have both failed to properly distinguish between types of anger and failed to admit its proper role.
So, having left behind the options proposed by the philosophers, we are left with option 4. Here, we recognize that since God is moved by His kindness, anger is a natural byproduct of that love. If God is not angry with the wicked, He is not really kind to the righteous. To be a lover of something is to be a hater of its opposite.
But let’s take a step back and climb the ‘ladder’ of truth by asking three important questions: Does it make sense to believe in God or gods? Is polytheism true? Must the one true God have anger?
First, does it make sense to believe in God or gods? Some might suggest that we need no belief in deity to maintain an orderly society. They might say it is enough to have utilitarian laws. But even if this were true, what would be the explanation for the world? How did it come about? Can all of reality be random? Can nature produce nature? When we start thinking like this, we fall into all manner of foolishness.
Second, is polytheism true? Polytheism cannot be true because a shared power would be a lesser power. There is an obvious unity to the world. Polytheism came about when great heroes of old were deified posthumously. Great thinkers have always known that there is one God. They were just ignorant as to His nature.
Third, must the one true God have anger? What sets us apart from the animals is that we are, by nature, religious. Religion is what brings order. But how can religion itself be maintained without fear? And how can there be fear if god is never angry? The anger of God is actually a virtue, not a vice.
Let us now confront three possible objections to option 4:
First, we must consider the ‘problem of pain’ (as Epicurus has made famous) and how it relates to God’s anger. If there is one true God, then why is there evil? The simple fact of the matter is that God allows evil for the greater good. It is because of the existence of evil that we are given wisdom to know and choose the good. The one cannot exist without the other. But if evil exists, it only makes sense that God is indignant (angry) when we choose it.
Second, Epicurus also objects that once we suggest God experiences affections like kindness and anger, we open Him up to all affections (like fear, sexual desire, etc.). But God has nothing to fear (since He has no authority over Him). And God has no (sexual) desire, for He is complete in Himself and is eternal (no need to reproduce). God has kindness and anger because he has use for such affections, given the diverse choices of His human subjects. It would not be kind for God to leave evil unpunished. He must be angry at evil.
Third, the stoics object by claiming that all anger is wrong or foolish. Because they failed to distinguish between just and unjust anger, they abhorred all anger. Fury and rage, no doubt, are unfit for God (and humans!). But it seems obvious that a good and just God will be displeased (and moved to action) against evil and injustice. This is just anger.
Let me respond, more briefly, to three remaining questions:
Shouldn’t God be too calm to get angry?
Surely God’s anger is not furious with rage, but it is personal (for He is our Creator and the world is His creation). It’s a genuine affection.
Why can’t God just wait for Judgment Day?
God is extremely patient, but His kindness is too great to do nothing about evil until Judgment Day. Besides, in many cases, God’s anger has led to transformation on our parts. Responding appropriately to divine anger is a way to avoid the wrong side of Judgment Day.
If God gets angry, why is it prohibited for us?
God does not completely prohibit anger. He forbids us to stay angry. We can be angry without sinning. Indeed, we should get angry at injustice (provided we find a healthy way to release our anger). God’s anger only lasts against those who continue in sin. When we repent and our morals are reformed, God’s anger passes away. This is God’s preference, for He longs for us to be in right relationship with Him.
Let me conclude with a passionate plea for the truth of God’s anger. All the Spirit-filled prophets have spoken both of God’s favor toward the righteous and anger toward the wicked. Fear of authority brings order to society. And where there is no anger, there is no reason to fear. It is proper for men and women to both love (because He is Father) and fear (because He is Lord) God. Consider both His kindness and His severity. And live in such a way as to never need to personally fear the consequences of His anger.