Arcite and Palamon have sworn an oath of brotherhood to one another, promising to defend one another's interests in everything. Yet the first we hear of this oath is when it's in danger of dissolving. Why might they break their promise? Because the love the same girl, that's why. Both Palamon and Arcite seem to think that romantic love is more important than bonds of friendship, and "The Knight's Tale" doesn't do much to question that point of view.
In contrast to Palamon and Arcite's fair-weather friendship, however, a brief passage just after their falling-out details the devotion of Perotheus to Theseus. Apparently, these guys are such good friends that they're willing to go to Hell and back for one another. So, despite the main, unsuccessful friendship in the tale, we do get an inkling that other, deeper possibilities exist for the bond between two friends.
The friendship between Perotheus and Theseus causes the reader to question Palamon and Arcite's decision to dissolve their bond.
Theseus's implication that it's better for a man to die than disgrace his friends reveal his view that the most important obligation of friendship is to bring honor to one another.