#2 Light was a Sociopath
One of things people buy into often is stereotypes. There is a difference between being called a sociopath and a real sociopath. Most sociopaths are generally good analysts.
One of the things most people say is, it’s okay to kill criminals. If I were to look at things from the inmate’s point of view, then there are reasons for their criminal behavior.
It was maybe the society that turned into one. Just like how Light changed with the Death Note. Economically speaking, it costs atleast $50,000/yr on an average to keep a single inmate in jail. He did the right thing be removing them off the radar, improving the economic condition of the world.
But, everything has a limit!!
He crossed the line, when he killed his father. Killing strangers is one thing, but sacrificing your family that too his father, just to protect his interests. That definitely makes him an evil psychopath.
Was Light a sociopath? yes, as he crossed the line after killing his family.