I somewhat agree with you on this. Only somewhat. You are correct that the son has the right to his feelings, of course. And it indeed seems that the mother wishes to erase the harsh feelings and pushes to do so, understandably as well. However, I am detecting a strong case of "beating mom over the head at every opportunity" syndrome, and here is where I disagree with the "right" to be angry. Being angry is one thing. Vomiting anger at every opportunity is another entirely. We can all claim our "rights". "I had a right to be angry", "I had a right to hit her , she pissed me off", "I had a right to touch that child there, she wanted me to", ad infinitum. Rights are tricky. When it comes down to lashing out at another in the name of "rights" that is a wrong. This son may have issues that are legit. Our parents hurt us. Our parents damage us. And there but for the grace of God goes you, and me, and him. This son does not appear to have the ability to attempt to empathize with his mother. I wonder if he has tried to really hear her explanations of victimhood and weakness at that time. To see life through her set of filters. We are given filters by our parents and life in general, there are many, and these filters determine how we shape our own environment. In great change there is a need to examine these filters. Where did they come from, do I need them, can I discard this one or that one, do I need to add one, etc. Our hurt children often stand on the mountain in judgment, incapable of seeing through anothers' eyes why things may have been the way they are. They are focused on the mental self-gratification of anger, which is a self-absorbed place to be. Now, I say it is legitimate to be there, to spank the monkey on it awhile is necessary, but to STAY there, for years, focused on your own angry pee-pee is another thing entirely, and the mother should not allow her dignity to be compromised one more second. This is another form of abuse that one can fall into: The guilt of what we did to our children out of our own inability to make good choices or have better boundaries tells us to hand our kids a license to express anger as long as they want. And often they will do simply that: be angry, use it as a filter in their own lives, as a license to heap abuses on others (and sometimes themselves), and never get to a point of releasing or dealing with it.
I understand being angry. But I think (and this is just what I think) that mother should make a decision to take responsibility WITHOUT GUILT, and shut down this boys expressing his anger any old time. There is a time to say "ENOUGH! I understand that you are angry with me, and you have good reason to be. But NO amount of anger gives you the RIGHT to treat me with disgust and contempt. I have paid my dues, I have attempted an amends, and I will no longer listen to you attempt to beat and abuse me further with your anger. I am seeking help regarding my role in my life and your life, and if you cannot deal with your angry feelings toward me, than perhaps you should seek a trusted person to talk to about your angry feelings. Because you are abusing me with those feelings, and THAT IS NO LONGER ACCEPTABLE".
She may deserve some anger, but she does NOT deserve CONTEMPT - those are 2 different things.
Now I will reveal that this has been my exact experience with my daughter. That is why I indentify. Once I stood up like a phoenix and said ENOUGH! (and yes, I risked the relationship), once I told her that SHE was responsible for her own contempt and anger today, and once I told her that she was welcome to ask me questions about why I did the things I did or didn't do in a rational, non-HATEFUL way, and once I told her that ABUSE IN ANY FORM, EVEN "JUSTIFIABLE ANGER" WAS NO LONGER ACCEPTABLE TO ME, it made a tremendous difference. I recall telling her, too, that I really hoped she was able to learn much from the mountaintop of judgment that she was on, because I will be real curious to see how much better SHE parents her kids of which she had NONE and NO EXPERIENCE as a parent to pull from. And to watch for the Karma Train, because it was coming, and right from the direction that her Judgement Finger was pointing. She has backed off of me, asked questions, and has removed quite a bit of her anger. She no longer holds me in contempt, because I no longer hold myself in contempt, and do not allow contempt to enter into my spirit today.
We all got hurt. We all got damaged. We do not get to hurt and damage because we were hurt and damaged. We don't have that "right".
To the mom I would say - stop holding your Self in contempt, let go of the shame and guilt, and quit chasing him down trying to get him to quit feeling what he is feeling. You can let him feel it without feeling it all over you, I think you allow it because you feel badly for whatever damage you caused. People will have no choice but to treat you differently if you release this guilt and shame. They really do only treat you the way you treat yourself, and they treat you however you allow them to. When you change this, he will have no choice, because you will no longer accept the contempt on any level. In the deep dynamic, he knows that you are accepting this at a personal level because you carry at your core the lie that "he is right". Stop it. You cannot change today one thing you did yesterday, but you can change right this second. You have control over right now. Nothing NOTHING will change what has been done. It is written in indelible ink in the book of life. But this very second, as you are reading your computer, you can change any negative thing about YOUR SELF that you want. Change YOU. Being 100% accountable is great. As a matter of fact, being 100% accountable should give you the ability to stand tall, look this child in the eye without shame and say yes, it was me, NOT grovel on the ground while he stands over you with that sneer in his face.