At it's best punk adovates egalitarian politics. At it's best punk fights against racism and white supremacy. But punk is best when it's small, local, and something to participate in. By rejecting a mass audience punk is able to better respond to speak in specific terms which its audience can relate to. By foregoing mass appeal punk bands are able to say things many people disagree with.
Mass marketing relies on conformity, millions of people buying the same products.
Punk is a refusal to conform. I think many punks are unable to understand how much of the dominant culture they have internalized. Sometimes it has been hard to keep independent projects going because punks have had a hard time working collectively. Many great 'zines, record labels, distributors and other resources have relied too heavily on one or two individuals. Punk isn't just an aesthic approach or a set of principles.