Why does the captain pointedly disagree when Silver calls himself captain?

The captain pointedly disagrees with Silver calling himself captain because it undermines the authority and legitimacy of the ship's hierarchy. By denying Silver's claim, the captain asserts his own position and reinforces the established order among the crew. This disagreement also highlights the tension and power struggle between the characters, as Silver's ambition poses a threat to the captain's control. Ultimately, it emphasizes the conflict of leadership and loyalty within the narrative.