This is an exercise to help you process anger from the abuse and trauma of the past in a healthy way.
It's normal and natural to be angry after abuse. This kind of anger is called "righteous anger" and it's caused when someone violates a boundary, hurts, uses, manipulates and abuses you. It's not the same as "toxic anger" which someone uses to manipulate and control someone else's behavior through intimidation.
You may notice PTSD symptoms of rage if you have a lot of anger built up over the years and decades. If you're depressed, you're probably directing that anger inward toward yourself.
We must release anger in a healthy way so we don't misdirect it toward something or someone unrelated to what we are actually angry about and so it doesn't eat our body alive.