I was gonna say that, actually. Dehumanising others for lacking empathy is, ironically, only demonstrating their own lack of empathy.
I'd argue that this is one way that people who lack empathy may be actually nicer people than those who experience empathy normally, at least in my experience. I feel like having complete empathy is impossible, the ideal of the "empath" honestly feels impossible. I feel like, in reality, people normally have selective empathy, and usually cannot empathise with those who they do not understand, usually due to some glaring difference between them and this "other". Hence why a lot of bigotry and tribalism exists in the world. They are used to going through life being able to empathise with others, so when they meet someone so different to them that they struggle to empathise, they do not know how to interpret it, and thus dehumanise these people and hate them.
In my experience with a lack of empathy, I basically had to learn that other people were humans like me. With complex thought processes, and complex emotions. The idea that people were not just mindless NPCs with pre-programmed actions was a big epiphany to me. As a result, I'd say that I'm less prone to dehumanisation, since I have the same amount of empathy for people, and had to manually learn that other people were human, rather than relying on some natural emotion or instinct. Granted, I'm not perfect, and it's more like a choice on whether to view other people as human or not (sometimes it really feels like I can just turn it off, or perhaps it would be more accurate to say that I can just choose to ignore that whole "other people are human" part with little to no worries if I want), however my point still stands.
People with low empathy have had to just navigate life in this state, learn to live and form relationships without feeling empathy for others, and thus I would argue that really, the whole "people with low empathy are violent" thing is just due to personal circumstance. A lack of empathy is usually caused by trauma, and trauma can lead people down dark paths, can make people more aggressive, easier to set off, meaner, impulsive etc. etc. as well as using substances to cope. On top of the fact that it usually means they are not in a good life situation, and so a lack of empathy coupled with these others aspects of being traumatised, and likely in a poor position in life, can lead to criminal behaviour or violence, particularly because if one's trauma has lead them to lose the ability to empathise it has likely also lead them to develop those other symptoms alongside that to begin with (aggression, impulsivity, substance use etc., likely due to the trauma causing them to develop one of the cluster B disorders). Because you usually don't see those with a lack of empathy in good positions in life (in reality, I highly doubt every politician/rich person actually has low empathy, I'd say they're just assholes) it is easy to see all this terribleness from those who lack empathy and say that they're all evil.
And I'm not alone in this line of thinking, James H. Fallon (a neuroscientist who happened to have psychopathy) said that he believed his relatively stable and good upbringing and life circumstances meant that he did not engage in the criminal or violent behaviour that one would expect from someone suffering from his condition.
Though for the record, the only cluster B disorder I have been diagnosed with is BPD, and I do not particularly believe I suffer from AsPD or NPD despite my low empathy, so while I am mostly commenting on pwAsPD and the symptoms associated with it, I do not have it as far as I know, I do not intend to speak as if I do, and I am also generally speaking about those who have low empathy in general too, although BPD and AsPD can overlap in a lot of ways.