Oh, it's not that I'm unsympathetic to the actual sentiment of "oh shit, I just wanted some happy pictures of my OTC, not people talking about how awful they are ;__;". I get that, I get people complaining about that -- but, piggybacking on what you said, it's the virulence and aggressiveness of the complaints that bothers me, combined with the implication that their character is the only one who ever gets that kind of treatment or who deserves that kind of defense. I think I'd be less inclined to roll my eyes at them if they were out to improve the fandom's tagging policies in general, policing the other characters' tags as diligently as they police their own, or if they even seemed to recognize that people hating on Ward is not a completely-unique-to-Ward phenomenon.

... but yeah, the way tumblr makes it impossible to separate personal and public space is a big part of the problem here. I do sometimes forget when I make posts that the tags are going to come up in a general tag search; I tend to tag for my own journal and not think about the wider context. I suspect a lot of people do. And OF COURSE people looking for character meta (both positive and negative) are going to peruse that character's tag, as well as people looking for pretty pictures and gifs. There's really no way to separate them out, with the way tumblr is organized.