Pro consumerism propaganda, makes us see a “fan” as a sane, innocent version of a fanatic. Instead of an enjoyable activity (that you don't care doing it for free), hobby defines obsessive behavior.
There is nothing wrong in being a collector, a fashion addict, a “geek” isn't there? Even when you know all the not biodegradable trash you generate “to be on trend” (i.e. the plastic of all your old smart-phones) ends up in your food you feel there's something wrong in not going in the same direction than the rest, don't you?
Capitalism could perhaps be the best deal for society, it's not the origin of consumerism, fanaticism is. In no case fanaticism is sane. Innocent “fans” have been the bricks any empire known from history have been constructed with. Empires always imply slavery.
What is fanaticism, then? Call it “fascism” or “religion”, fanaticism is apathy, laziness in the sense of not be willing to accept the responsibility over our own actual point of view, based on our own knowledge, experience, intelligence. Simply put, fanaticism is the denial of thinking. If it exists, in this life, in this world, something we can call “independence” or even “freedom” it's what we get through our own honest thinking. Fanaticism means to renounce that independence and freedom in favor of a false sense of comfort and security.