“My dear Professor. . . [a]ll this ‘You-Know-Who’ nonsense—for eleven years I have been trying to persuade people to call him by his proper name: Voldemort.” Professor McGonagall flinched, but Dumbledore, who was unsticking two lemon drops, seemed not to notice.
Dumbledore’s impatient reproach to Professor McGonagall occurs in Chapter 1, when they and Hagrid appear in front of the Dursleys’ house to discuss the sudden tragic deaths of Harry’s parents. The passage reveals Dumbledore’s composure even after a hugely traumatic event like an evil wizard’s murder of two innocent people: he is calmly using phrases like “My dear Professor” and eating candy, while McGonagall is flinching with nervousness. We see clearly why Dumbledore is head wizard and McGonagall his subordinate.
The passage also reveals the importance of facing one’s enemies directly. For all of McGonagall’s education and expertise, she is unable to speak Voldemort’s name out loud, as are many other Hogwarts residents. The implication is that they are too scared to utter the name. Harry, we find out later, is, by contrast, not scared at all; his friends keep urging him to say “You-Know-Who” instead of “Voldemort,” but he sees no reason to do so, and keeps forgetting. When Harry calls Voldemort by his proper name, we get a hint that Harry will be the one who can face the evil wizard directly, as he in fact does when he stares at Voldemort’s face on the back of Quirrell’s head. Harry’s directness is exactly what Dumbledore is asking for from McGonagall and symbolizes the importance of confronting one’s obstacles.