Epistemic status: provisional.
What is the nature of God's anger, in MSLN?
Why would God be angry? One reason is because God values his creatures highly and doesn't like to see us disvaluing / disrespecting them. (Respect is inherently part of love.) We like to think that love would love us (approve of us) out of an abundance of love, but it is also possible that unless we are the most innocent and/or oppressed creatures, love would be angry at us out of an abundance of love, for what we do to those most innocent and/or oppressed creatures. This deviation from love/respect/valuing is (perhaps) the essence of being out of tune with God, of violating legitimacy.
I think God might become angry if we disrespect him or disvalue him. It's odd to think of a loving being caring about its honor, and perhaps God does not. However, God does care about the truth, and we sometimes lie to ourselves out of disrespect of him. God is worthy, and to not respect him is to not be in tune with the truth. And disrespect is something that in itself is angering, no matter who the object of it is. So I would think that God would be more angry when we disrespect his creatures, who are weaker than us, and than him, but still angry when we disrespect him. I would think that God regards ego respect less highly than survival respect.
God, knowing everything that can be known, knows what he's doing when he is angry with us, and because he is legitimacy (he bears all the burdens of the world he created), he is fully justified in being angry. But we are not. Anger may be a helpful thing, one which, from a consequentialist perspective, is sometimes better than not being angry. But it is dangerous and we exceed our rights when we are angry. Sometimes anger has little or no redeeming value.
So far I've been trying to talk about God's response to present states of our hearts (when we disvalue/disrespect/fail to love). But just as we can be angry over the past, so can God be. How can that anger be alleviated? God can't experience rest if he is angry.
One possible answer is that the injustice of past violations of legitimacy / sins can be alleviated (God's mind healed so that he is no longer angry) by there being some kind of atonement, some kind of payment for transgressions. We might think this strange. We find ourselves able to forgive people without there being an atonement.
Forgiveness (a letting go of anger) might only take the other person coming to see things as we do, which validates our point of view. Sometimes we are angry only because we are invalidated. The person doesn't matter, simply the lie that they told about us or about life, which we somehow can't refute unless they somehow undo the lie, which was told in a past behavior, which violated us.
Or perhaps it could come about that we simply forget the other person, take them less seriously in some ways. We have the virtue of forgetting.
Can God forget the past? If not, then it always exists, as fresh as ever. I'm not sure why God wouldn't forget the past. Certainly he must cease to experience our past experiences in an omnisubjective way, in order to experience rest. So probably he can and perhaps already does forget some aspects of the past.
Do we think of God as someone who knows the truth? That seems like something we would expect of God. The truth might include the past. Not a past out of proportion to the present, and not isolated parts of the past, as we experience due to trauma or bitterness. But a truth that can't discount past sins any more than it can discount present repentance. Perhaps, just as we possess an intellectual though not experiential knowledge of what is, God does as well, and this intellectual awareness can never forget. In the Bible, "the smoke of their torment rises forever and ever" (Revelation 14:11) -- the memory never fades, but does not become anything more than a memory, and does not cause God unbearable pain, as the fully omnisubjective knowledge / experience of the past would.
God can forget the past (cause it to cease to exist by not being aware of it, as long as as it's not held onto by any of his creatures), but not whatever facts are needed to explain the present, that which is part of the concept and the simantic words of presently existing beings. The sensory experience of unbearable pain must involve unbearable pain, but no concept necessarily involves any unbearable feelings. It is always (I think?) possible to conceptually grasp something without feeling unbearable pain. The conceptual grasp could theoretically be separated from any unbearable pain that for whatever reason might accompany it. It might be necessary to perform some kind of work to make that happen, but it is possible.
Perhaps there can be something unbearable about the intellectual remembering of past violations. This seems true to (human) life. It seems possible that God could let go of past injustice if there was some kind of atonement. I think this makes more sense if you think of the "need for justice" as being some kind of body part, like a broken arm, which a person needs to deal with, as opposed to something that flows deeply from who they are. So God has to deal with his "need for justice organ" and sends his son as the healing sacrifice of atonement.
It's fair to see God as being obsessed with justice, in a way that we are not. It may be the case that if you're really in tune with reality, you should be obsessed with justice. Truth is reality as a whole, and injustice is a problem with reality as a whole, how things don't add up. It may be that to be a (literally or effectively) infinite being, in tune with reality down to the finest details, or the bare metal of it, you have to be obsessive. And obsessiveness is not an evil thing, thus not incompatible with being God -- albeit something that if taken to a strict / real degree has the potential to produce unbearable suffering.
In that case, God's responsibility to / indexing to / connection to justice could be so intense that he couldn't get over his anger at us for our disvaluings of his creatures (and him) which we did in the past, and thus adjust his concept of us enough that he could forgive us. This would make it hard for him to get close to us on a personal level. So he would seek some way to help him overcome his anger, following from his obsessive connection to things being the way they were supposed to be. He could send his son to die, to pay the price of his justice, allowing him to be free from his need for our sins to be paid for. Apparently, no therapy was available for God but, like in the case of someone undergoing body modification (surgery, hormone therapy), to treat the mental condition of gender dysphoria, it was possible to reshape external reality in a therapeutic way, through the Son's sacrifice.
It makes a bit more sense to me, when thinking about the atonement, to think "yes, God sent his son to die, but it was really his son's idea". Just like "yes, God presents the simantic word of temptation to us, but it was really Satan's idea." In either case, God might have known that it was necessary, and set up the situation in which Satan or the Son would take initiative, but they were needed to do something he couldn't do, by their willpower. I feel like if I were in God's place, understanding that I needed to heal my obsession with injustice by seeing an innocent sacrifice die in place of all the guilty creatures, it wouldn't heal that obsession if it was fully my will that the sacrifice go. The sacrifice would have to volunteer. I couldn't just "let go" of people's sins -- that wouldn't require a sacrifice. My (if I were God) perfectly effective will could easily secure that without a sacrifice. Something would have to go beyond my will, and that would be the willingness of the sacrifice.
In the Bible, Jesus says "Father, let this cup pass from me. But not my will, but yours be done". To be fair, this sounds like a flat contradiction of what I just said. It sounds like the Father was the source of will, and the Son simply had to learn to submit. But I can imagine that the healing began with the Son's volunteering to die, and that it simply had to be seen through someday to carry through the intention. Jesus, as a human, really was willing to die, when he said "not my will, but yours be done". He was faltering in his intentions, but ultimately Jesus died doing what he set out to do, even if, in a way that might be familiar to humans such as us, he was terrified by the actual prospect of doing what he really wanted to do, and had to be helped by an iron commitment, based in a connection with someone outside himself. Then, once Jesus died, God could look back and say "It's over, it's all paid for, I (and a large part of reality) are healed."
So then, there is a perhaps intense poignancy about the Son dying for the Father. We have tended to focus on what it meant for us, how we benefited, but there is more to the story, I think.