We see the reactions of everyone around him. They're confused or disturbed. The movie says Peter is not cool here, even though he thinks he is.
The following video, which replaces the music with normal streets sounds, shows people's disgusted reactions even more clearly. And yet when this video's shared, I've seen people act like it's The Big Bang Theory without the laugh track, act like it reveals some weakness the movie wanted to bury. Nope: It just emphasizes the truth you were supposed to see all along.
The street scene is very useful in that it tells you to distance yourself from Emo Spider-Man. It's also a bit of a cheat. Because Spider-Man 3 is not the story of someone who considers himself cool but who everyone else spurns. Other than in this scene, nearly every character finds Emo Peter just as enchanting as he finds himself. And yet the movie wants the audience to consider him ridiculous. That's hard to pull off, but the movie manages it.