When the more mature one the fight tries to resolve it, the problem can be compounded if the other one has serious anger issues. Its funny, some people can only express one emotion well, that is ANGER. Generally people who are neglected, physically or emotionally abused, with severe problems in their self esteem, body image etc. sometimes suffer from these anger issues. Anger is a kind of defensive mechanism to protect you from the real feelings. So the person lives in the false sense that everything that is happening is the other person's fault with so much conviction. The thing they don't realize is that they are very obviously hiding from the real truth and that the anger burns them far more than the people they are throwing it at. The problem, as with most things, this habit once formed just becomes a self-strengthening loop. In any self help article, the common theme is, 'face the real visceral feeling without the shield of anger'. That is how you truly overcome past pain. Another problem is that, even if you tell them this, their denial and ego would kick in. Thoughts like "I'm listening to this person who tortured me etc. Whats up with me? What can this
I think the only way to deal with this is to melt them with your nice behavior and avoiding deeper and personal conversations. If you get angry, then you're lowering your consciousness to that level. So my approach might be, watch yourself when you react to this person, use your evolved reasoning and insights to prevent a lowering of your state. What comes out a person's anger is more about the person's anger than the content of what is said. The content that comes out is usually an exaggerated slanted version of all the bad things you did.
Let me attempt to put it in the real context. The allegations represent a very tiny portion of reality in proportion to everything that you are. Secondly, since the person is filled with anger, a distorted, slanted, exaggerated version is created of that tiny fraction. Thirdly, it represents the past which is imaginary in the context of this moment. You might have reacted that way in the past and it might have been the best approach considering your STATE(level of knowledge, personal interests, priorities etc.) at that time. That state might be irrelevant now. So at every level getting severely affected by that person requires you to revisit the context I have described above to dissolve the past conditioning or habit.