I love you...romantically.

People see what they want to see. Perhaps people who find gay aspects of platonic friendships are projecting? Why do people insist on interpreting straight relationships as gay? One idea is that people are uncomfortable with intimacy without the presence of physical intimacy. Skepticism leads us to believe that nothing can be as simple and innocent as it appears, when we apply this view to friendship we develop twisted theories about people's true intentions. This same process guided the actions of Mortimer in Edward II and convinced the editor of "Brokeback Mount Doom" to manipulate video footage to project eroticism where there initially was not overt sexuality.
People also label men as gay when they do not abide by the social expectations. When men are forthcoming with their feelings, or flagrant as was the case with Edward II, people want to associate them with effeminacy and portray them as gay. This kind of categorizing is really a way for people to find structure when they are uncomfortable with someone else's behavior.
On a slightly different note, the Tropic Thunder fake promotion "Satan's Alley" follows a similar, though slightly more direct, theme.