“Apart from warlike activity proper, the institution of the duel is also an expression of the same superior readiness for combat; and the duel is a leisure-class institution. The duel is in substance a more or less deliberate resort to a fight as a final settlement of a difference of opinion.”
"The boy usually knows to nicety, from day to day, how he and his associates grade in respect of relative fighting capacity; and in the community of boys there is ordinarily no secure basis of reputability for any one who, by exception, will not or cannot fight on invitation."
Of course, the average boy outgrows this phase, but
"...the leisure-class and the delinquent-class character shows a persistence into adult life of traits that are normal to childhood and youth, and that are likewise normal or habitual to the earlier stages of culture."
So Veblen seems to see the aggressive, predatory nature he attributes to the leisure class as being childish. In the case of duels, I'd have to say he has a good point.