Why does The thief address Jonathan what seeming friendliness and familiarity

I think the friendliness was the leader thief's way of being arrogant. The leader's language suggests he is less educated than Jonathan, and his glib, arrogant tone reveals his awareness of how little a family has to rely on outside themselves. Though he doesn't commit any acts of violence, the thief leader represents the ever-present potential for violence in the unstable post-war period.