Yeah the fact that there are quite a lot of people that can belittle, bully and intentionally hurt others without feeling an immense guilt is something I have a hard time understanding as well.  But I followed a course last month that discussed this topic:

From an evolutionary perspective you could say that intentionally planning to hurt others by bullying/belittling them or just straight up planning to murder them is a useful survival strategy in oder to gain more social status or resources.  High levels of Empathy would make commiting to this strategy a lot harder though, because feeling guilty and experiencing the others pain will stand in the way of you hurting others. There is actually quite some research showing a link between low empathy levels and instrumental aggressive acts like this. I think it's strange that humans have an entire brain circuit dedicated to empathising with others (when we see someone in pain certain parts in our brain's own pain circuit show activation as well), but at the same time can unconciously ignore this information and hurt others just because its benificial to them in the current situation...

Oh yeah and a lot of current research actually seems to suggest that there actually is NO dysfunction in empathy of people with ASD! Just because we might not show or experience it in the same way as others do does not mean that we lack it :)