If I get mad at you, it’s because you’ve hurt me badly, have never tried to make amends and I have a good goddamned reason to be hurt and angry after months of your denial and defensiveness.  

If you get angry at me, no matter when, it’s because you are being fucking unfair and vicious, for your own sick, irrational reasons.  

What is hard to understand about any of that?  Could it be clearer?

Now, all you have to do is convince the eye witness who loves you that what they saw, what you experienced, actually happened.  Since everyone has their own perspective, aren’t we really all arguing that we’re better than the person who claims we treated them badly, that our point of view is more valid than theirs?  Isn’t everybody just equally right in their feelings?

No.  There are objective things that actually happen prior to and in the aftermath of somebody getting angry.  Focus on those, compare how each party acted.  Things that actually took place won’t lie to you, no matter how emotionally compelling a spin is placed on them.