I wrote about this. Anger is part of coping with grief and it can be useful. It motivates you to investigate and find the truth. It clarifies your personal rights that were violated and helps you learn how and when to stand up for yourself in the future. It drives you to stick up for others. It helps you see clearly what actual moral values are.
If you hold on it too long--let it fester--all that energy will begin to turn inward as destructiveness. You'll start to feel too much like a victim and not like a survivor. You may have malevolent thoughts of revenge. You may even desire that revenge so stronly that you become willing to invent crimes the borg did just to quench your thirst for character assassination--a weapon used by the powerless.