If you took your lessons from TV, (where people are depicted in broad generalizations), then all nerds (or geeks, whatever you want to call the people who like the type of things we like) are part of one giant group. Apparently we all go to Comic-Con, we all dress up in costumes, we all read comic books, we all love science fiction, we all play endless games, we all play D&D, we all love Lord of the Rings movies, etc… But it isn’t true. Some of us like some of those things and some of us definitely do not like some of them.
In contrast to this strange media depiction of one giant, inclusive community of nerds, in many circles there is a pretty exclusionary attitude towards the other circles of fandom. While it isn’t very extreme (there aren’t Warriors or West Side Story style confrontation going on at conventions between Doctor Who fans and Game of Thrones fans… even though that would be very entertaining) there is a fair amount of animosity. One group will often have little or no understanding of what the other groups are into, and we can find it quite insulting to be lumped into one amorphous “nerd” banner. This kind of division can seem random from the outside, but it is nothing new, and certainly isn’t isolated to our culture of fandom. It has always existed within politics, religion, sexuality, etc. People like to be acknowledged for their unique features, not randomly labeled in ways they do not identify.