It's unclear why Settembrini harbors such disdain for Behrens and Krokowski. As medical doctors, they’re technically in the business of improving and sustaining human life, which the humanist Settembrini should approve of. His mocking of Krokowski’s black clothing and air of self-assurance perhaps suggests that Settembrini despises the doctor(s) for their self-importance. As doctors, they effectively act as gatekeepers between life and death, and they become gods in a sense. Settembrini, with his humanist respect for democracy and human progress, would resent such a hierarchy—to him, it’s no different than religious authorities using the threat of damnation to subdue the masses.