Isolation and disconnection from society aren't the same thing as a lack of compassion. There are plenty of people who don't have the social skills to interact with the greater part of society, this doesn't make them compassionless, just kind of lonely.
Measure a person's compassion by their actions, not their situation. Parson treats Bogroll and Sizemore as equals, despite the fact that most of Gobwin Knob - particularly Stanley - look down on them. When he encounters Misty, he tries to engage with her as a person, despite the fact that she's only been treated as a thing by everyone around him. Even after being told what a horrible idea talking to the Eyemancers individually is by Wanda, he keeps trying
until he finds out that it could kill the casters
. He mourns the deaths of Misty and Bogroll...
Parson's not perfect, he isn't a saint, he doesn't always act with perfect compassion, but he's demonstrated a capability for compassion that no one he's surrounded by - save Sizemore - possesses. This compassion won't always win out against his desire to win, but that's what makes the story interesting.