Leadership: Service vs. Sociopathy. Discuss.

So, business school (successfully) taught me the lesson that leadership is a service-oriented discipline. That is, you provide leadership by serving the people you lead. I've seen this play out at my current workplace and it makes sense to me.

Similarly, there's a lot of discussions about executives-as-sociopaths, and how there are not only strong correlations between executives and sociopathy, but it's a requirement of the job because it allows for faster decision-making, etc.

I'm trying to reconcile these. Any help would be appreciated.