General question, is the pejorative connotation to Otaku a recent thing? Is it's pejorative connotation in the West a recent thing?
I was pretty heavily involved in the DBZOA (DBZ Otaku Alliance) many, many moons ago, and after it was rebranded as the OA (Otaku Alliance) and I don't remember the same negativity associated with the term. Of course, this was a very different time and the popularity of anime in the US especially was still limited to episodes of DBZ and Sailor Moon on Toonami.
Correct me if I am wrong.
Otaku mean someone who like or too passion toward something to the point become obsessive.
It not only for anime or manga. But then the term change to associated with people who like anime, manga, games, action figure, idol, ect.
In japan it's a negative term and feel with negative stereotype. They treat like an outcast to Japanese society. Maybe recently the society began to accept and acknowledge them.
Outside japan is not negative as japan because people doesn't care or don't know the true meaning over it.