The poem's central character, Martín Fierro, is a gaucho, a free, poor, pampas-dweller, who is illegally drafted to serve at a border fort defending against Indian attacks.
In particular, he describes it as sad that his countrymen read "with indulgence or admiration", rather than horror, the famous episode in which Fierro provokes a duel of honor with a black gaucho and then kills him in the ensuing knife fight.
Borges is somewhat less impressed with Estanislao del Campo, author of Fausto, whom he characterizes as the most rural of the gauchesque poets in his diction, but the least comprehending of the mindset of the pampas-dweller.
Borges is in more sympathy with Calixto Oyuela, who sees Martín Fierro as a tragic lament for the passing of the gaucho life and the fading of the Spanish-descended criollos into the emerging multi-ethnic Argentina.
Borges mildly rebukes Miguel de Unamuno for denying the specifically Argentine character of the work, annexing it to Spanish literature, and is absolutely scathing on the subject of Eleuterio Tiscornia.
Tiscornia's excessively academic and Europeanizing approach to Martín Fierro produced a footnoted edition of the poem which Borges finds, at points, laughably misleading.