Belz...
Fiend God
But no level of disinterest that removes the title of fan. Apathetic fans get to still be fans.
No, that's in the name: fanatic.
If you claim to be a fan of a particular sports team, but never watch their games, buy their merch or even talk about them in any positive manner, people will conclude that you are, in fact, not a fan. The evidence contradicts the claim.
This isn't rocket science. In fact, you can take it as a principle, which now means you must apply it to its logical extreme.