Final answer:
Rainsford's statement about a superstitious sailor reflects the theme of fear's psycholgical impact and its contagious effect within a group.
Step-by-step explanation:
When Rainsford says, "One superstitious sailor can taint the whole ship's company with fear," he means that a single person's irrational fears can infect a larger group, causing widespread unease and panic. This idea reflects the broader theme of the psychological impact fear can have on a group of people. In literature, this can be seen as a commentary on the contagious nature of emotions and the human tendency toward collective behavior.