We prefer to believe that children will never be forced to deal with an abusive parent. Sadly, the truth is that children who have an abusive parent will almost always have to deal with that parent at some point in their lives. When they are deemed 'old enough' they will face this situation without the security of another adult serving as a buffer. Children will have confusing emotions if they are the child of an abusive parent. Pretending that there is a magical way to 'protect' children from the feelings that abusive parents caused is never enough to address the issue.
When a child doesn't demonstrate fear or aversion to a parent.
Most children experiencing abuse will adopt a type of Stockholm Syndrome. This is basically where the victim begins to feel profound levels of empathy for their abuser. Children are much more likely to experience a conflicting sense of loyalty to an abusive parent. At times they deal with this conflict by justifying the abusive parents behavior as something always caused by external sources. This allows the child to identify a cause to blame without placing blame on their role model. While others may find the excuses absurd, the child who is making them believes the excuses are completely valid. It is simply too emotionally destructive for the child to face any other truth, so they will adamantly hold onto anything they can use to soothe deeply conflicting emotions.
When a child does not quickly recover from the damage caused by witnessing domestic violence.
For the most part, children witnessing abuse express comparable levels of behavioral and emotional issues to children who are sexually assaulted as minors. The emotional damage to children who witness domestic violence does have direct correlation to an increase in health and mental illness concerns even as adults. This effect is seen irregardless of if the child was physically harmed during any of the attacks. The emotional damage is extensive and will require treatment even if the child is completely removed from the abusive environment.
When a child turns on a non-abusive parent
Sometimes children find themselves so confused by the abuse they experienced that they express this anger by refusing contact with the parent who is not abusive. This is known as Parental Alienation Syndrome (PAS). Occasionally, the internal conflict of loyalty between two parents creates such emotional distress that siding with an abusive parent calms some of the pull to 'pick sides'. Siding with an abuser will temporarily stop the abuse and can create a sense of peace for children wrestling with these conflicts.
When a child acts out violent behavior
Children don't have the skills that adults have that help them determine what is right and what is wrong. All humans learn about social cues and expectations by living and experiencing life. A child that experiences violence as a normal part of relating to others, will naturally view violence as a normal response to stressful situations.