Why would Henry lash out at his comrade in this way?

Henry doesn't like to listen to over confidant soldiers filled with bravado. The loud soldier, who we learn is named Wilson, comes up to Henry, spouting exciting, confident statements about the upcoming battle. "We'll lick 'em good!" he repeats. His joy at the upcoming battle irritates Henry, who says bitterly that Wilson must think he will do great things. Wilson replies that he does not know if he will do great things, but he will fight "like thunder." Henry then challenges Wilson, saying that he may well run when the battle comes, and that he is not the bravest person in the world.