People who use violence to cope with their mental illness are in dire need of psychological help. Blaming individuals for actions that are a product of their mental illness rather than urging them to seek help can cause them to be more violent. It is important to educate people and bring awareness regarding mental health and the problems that can arise if untreated.
Narcissism, low self-esteem, or egoistical traits are sometimes the products of life long trauma, abandonment, and other mistreatments towards an individual.
Several studies show that 31% of people with psychiatric disorders and substance abuse disorders committed one act of violence in a year. Such patients, if not treated, can cause more harm to society. 
Violence is not simply irrational but acts of coping mechanisms by mentally ill people. Deeming such acts as "always wrong" demonizes people who struggle with mental health issues beyond their control and may prevent people from getting the help they need.