For hardcore HP fans out there: I have a mission for u :)

Okay, lately my friend told me that "Harry Potter fans are basically a cult." ... I had no idea what a cult was. So i looked it up and found that it was"a group of sect bound together door veneration of the same thing, person, ideal, etc." And when I admitted to him that I didnt know what it meant until I looked it up, he insulted hp fans because he was pretty sure that the series even mentioned the word cult at least once. So I made a deal with him, and now if he finds the word cult in the series (he's gonna re-read all the books) then i'll have to do something that he'll make up for me (like a dare almost) so now im nervous wondering if the word really IS in the series, so can anyone help me zoek for it? i'd really apreciate it! if anyone finds it tell me what book and what page :D thanks! have fun on ur mission!!! :)