I volunteer with traumatized kids, and I have sometimes met the offenders and the idea of evil is a complex one for me.
I think one way to look at it is to compare things with event that are accidents or something harmful that is done by someone we also see as innocent.
I'm not sure how to word this well, so if this is just a confusing mess of words, please ignore.
I hate to use terrorism or the US as an example, but it is an easy example. Terrorists have a huge impact on people. They physically harm a relatively low number of people living in the US, but Americans are fairly impacted by them pyschologically. Things like car crashes impact way more Americans, but not as many fear driving as they do terrorism.
I think the difference is that car accidents are traumatic and terrible, but usually not intentional. (I have been traumatized by car accidents so I'm not meaning to minimizing that kind of traumatic intent.) Terrorist threats are done with what the threatened party often sees as evil intent, and the threatening terrorist does seek to cause psychological fear.
A much less extreme example: if someone bumps be in the grocery store by accident, its not a big deal. I would be over it quicker than it happened. But if someone threatened to bump me in the grocery store, or they express or act with what I know to be intent to bump me, I would be a little afraid of them.
There is also the peri-traumatic environment in which the event occurs. The trauma therapist I had in intenstive treatment said that one of the biggest predictors as to the effect of a traumatic event will have on a person is the environment in which the traumatic event occurs. If it is a validating supportive environment, people tend to get better faster. If it is an invalidating environment, people tend to become more symptomatic and those symptoms last longer.
Applying that to the grocery store example. If the person bumps me and bruises me, I say ouch, and the person says sorry, and acts with validation, apology, and compassion, I'm likely to fair better. I might even develop a good relationship with the person.
If I say ouch, and the response is denial, blaming me, or telling me I wasn't bumped at all, the impact is different. The relationship with me and the person is harmed more.
Behavioral "accidents" happen and can affect us, even traumatize us. Sometimes they can even feel like they were intentional, and the thought that the accident was on purpose can affect us more.
Why? Because I think many people fear an intent to harm. Perception (accurate or inaccurate) of a capacity for that, or a capacity for evil affects our response.
Most people believe children are not evil.
Children are usually seen as innocent. If a little kid came and stompped on my foot in a temper tantrum and call me a poopy-head I'm not really traumatized by it. My foot might hurt, but I see the child as an innocent kid, unable to always control or regulate behavior and etc. I wouldn't fear the child or have a worse relationship with the child.
If an adult came up and stepped on my foot and called me a sh*t-head, it would freak me out a little and it would for sure affect the relationship with me and them. I see the adult as making a deliberate choice to harm me, and I think maybe we see adults as having the capacity to cause harm with intent in a different way, because most people do not assume all adults are innocent like children, and they have more power.
Most people do not equate terrorists with innocent either. But someone who does something that we also see as innocent, it can have a different psychological impact.
I have worked with two kids who have perped on other kids... Not just temper tantrums, but have acted in manner that was criminal and traumatizing.
I have no answers. Just random-ish thoughts and I struggle with this myself in so many ways. I have a hard time grasping that my abusive father intended harm. I know he harmed me. I have a really hard time accepting that he meant it. It feels like that would change it... but at the end of the day, intentional or evil or not, it still harmed and traumatized me very deeply and destroyed our father daughter relationship.