In "Heart of Darkness, who said, "Because the method is unsound"?

The station manager says this while trying to discredit Kurtz. He calls his methods for gathering ivory for the company unsound and lacking judgment. Although the manager doesn't "deny there is a remarkable quantity of ivory—mostly fossil." He adds, " We must save it, at all events—but look how precarious the position is—and why? Because the method is unsound." Marlow is not impressed and the station manager then tries to make Marlow "unsound".