True, that and the fact the sociopathy and antisocial behavior are a spectrum. A much larger number of people have antisocial traits than any kind of real pathology. Perhaps Joran was on the outer edge of what the Commission would consider acceptable and the symbiont unexpectedly amplified those traits.
It could be much like the situation with Edison/Krall, where there were some latent situations that might have never become genuinely problematic. In Edison's case it was getting dumped on a planet with dubious life-prolonging tech, while in Joran's case it was getting Joined.