Music snobbery comes in many forms, but it operates under two basic principles.
The first is that a hipster assumes that they know about bands you couldn't possible know about and therefore you are much less hip than they. Secondly, once everyone knows about a band, their music or their "hipness," is no longer viable as they have "gone commercial."
Jimmy Kimmel has done a social experiment. When a camera and a mic are present, what will they say when asked about fictional bands?
The result is a scream: