It seems for some folks their greatest joys come from harming others. What would cause a human being to sink that low?

Yes I agree.. i don't understand it either... but there sure are a lot like that and it seems more these days than ever.. we live in a society where hate is increasing rather than decreasing.. Funny you would have thought we would become more and more civilised and respectful rather than retreating back into ignorance and uncivilised behaviour..

Ego.

Twisted ego.

Some people are constitutionally incapable of feeling the same things we feel as human beings.  The idea of honor stemming from love, escapes them entirely.  They do not feel any positive feelings from the reward it brings.  They have no sense of what it means to have integrity and the strength of purpose it gives one.

They have nothing. They have no foundation.  They can't feel in a normal way.  So, they go nuts. They are actually jealous of people who have paths the sociopath cannot grasp nor share.  To fill the emptiness they have inside that knaws at them continuously, they fill it up with acts of revenge.   They also use people to get what satisfies them on some level.  Money and power.