When I was much younger, I used to have toxic anger problem. And I realized that much of that anger was selfishness. I got angry because I wanted people and the world around me to be ordered according to my wishes. So, when I can't have it my way, I'd throw an immature, spoiled, childish act: shout, pout, say negative words, throw a tantrum, get physical, or start getting even. Part of my healing was to deal with that part of me that produces toxic anger and response to realities in destructive ways.
People who don't care don't bother to heal from their toxic anger. Most of us, however, would like to heal from this and stop it in destroying our selves and our relationships. But usually we have no or little understanding why we have it, how to control it, or keep it from doing continuing damage. So the beginning of cure is to explore it inside us and see what can be done about it.