I once did pretty much all of the same shit I now will not tolerate. In recovery, I am unlearning and growing, not pretending as if I have not been guilty of some very unfortunate attitudes and behaviors. I began my journey into recovery in my early 40s. Before that, I could be pretty assholey. When we know better, we do better.
If a person is bringing up things you did long ago to discredit you, chances are, that they are attempting to deflect attention away from their own current behaviors and actions. Offer them the chance to resolve the thing they are still upset about, but if it is only being used as ammunition, they want war, not resolution.
I realized recently (possibly) why people like my sister and ex prefer states of war to working together toward resolution and peace. Those require mutually agreed upon terms. They are not interested in mutual regard. Collaboration and compromise tend to lack appeal for certain types: making them feel less powerful, less in charge. To those people, I offer space.