The last section on "Imaginary universes" seems out of keeping with the rest of the essay. Articles about things in imaginary universes are usually very well maintained and monitored by a high number of users. Conflicts rarely serve as distractions and, since we are not paper, they do little to harm us fiscally.
The following sentence makes obvious the real reason for you dislike of these articles, elitism: "The harm is mostly the maintenance of large numbers of pages, and to our reputation: a serious encyclopedia".
Ultimately, and sadly, it is not hard to imagine that more people wish to read about [[Bulbasaur]] than [[Operation Barbarossa]]. I, personally, am not a fan of Pokemon at all, but I certainly don't object to articles on Pokemon characters if they are factually accurate and verifiable. These articles are of great interest to some, they bring thousands of users to Wikipedia and they do no harm. What is more, no other article will *ever* be placed at Bulbasaur or Pikachu and, if they were, a simple disambiguation would be required.
With all this in mind the only reason I can see for your objection to them is that traditional encyclopedias would not have such articles. Traditional encyclopedias would not have the space or the expertise for these articles. They did not need or want to appeal to teenagers and teenagers interests, we can and do.