Violence of all forms is wrong because it can result in lifelong consequences. Experiencing violence firsthand can have a physical impact such as permanent physical disability and psychological distress, leading to long-term mental illness.
Students who experience bullying, sexual, sexual, physical, and psychological violence at school are prone to developing weight disorders such as obesity, undereating, or self-destructive habits (self-harm, smoking, etc.). Such students, when they grow into adults, find it difficult to cope with normal life stressors. They tend to isolate themselves, avoid confrontation, or become obsessed with constantly pleasing people to avoid conflict. 
The violence that happens on a larger scale, such as war, genocide, bombings, and mass shootings, disrupts nations' development and well-being. Such conflicts result in a high mortality rate and disability. The consequences of war stretch beyond mortality and extend to endemic poverty, malnutrition, economic/social decline, etc. 
The passive consumption of violent events through social media and news coverage can lead to psychological distress such as depression, anxiety, and posttraumatic stress disorder (PTSD). One may not develop a psychological disorder through media right away, but it does lead to feelings of sadness, grief, and anger.