In my experience, 90% of the time it's an innocuous question to make conversation. It's normal to ask someone who their favorite character from a show is, or what their favorite album from a band is.

The other 10% is because people are overprotective of their hobbies. Part of it is because of the recent subversion of fangroups, but it's also because poseurs are annoying. It's disheartening to be really passionate about something, possibly be bullied because of it, amd then have it worn as a cheap, trendy fashion item by people who don't care at all about the thing. Anyone who doesn't fit the mold of your fangroup is going to be vetted. The more stink that they kick up about it, the more they look like a poseur.

I think that this whole issue comes down to women not understanding men's social hierarchies and interactions with each other. Men value competence and knowledge in the fields that they form social groups around. They're perfectly willing to accept a newbie at the bottom of the hierachy, but if you act like hot shit, without being able to back it up, you'll be rejected.