This post is an extension of a related thread on meta: Does your decision to upvote/downvote depend on the current score?
The above discussion mostly focuses on the phenomenon of upvoting questions and answers that one feels have been unfairly downvoted, or received insufficient attention, even if one might not have upvoted them purely on the posts' own merit.
However, I am interested in the reverse behavior: one sees a very popular post which seems to be pretty mediocre, but is not an intrinsically flawed question or answer - it just doesn't seem to merit its current popular status. Is it acceptable to downvote in such a situation?
The question is somewhat well-defined, but it's not all that interesting, and really quite easy to answer with a graphing calculator. I don't want to see this sort of thing when looking for captivating geometry problems, and I would have been happier if it had been lower in the queue so I could have instead seen better questions. I think MSE would be a slightly better place if it didn't implicitly present this question as the second-best out of 40,000 geometry problems on the whole website. And the user hasn't done anything else on MSE in the past decade, so I'm not likely to hurt their feelings.
Nowhere in this thought process is a judgment that the question is actively bad, or that it would merit a downvote if it was sitting at $0$ in the new queue, but it does present a case for downvoting the post as it currently is, so as to bring its score in line with what it "should" be.
In this particular case, the question is closed and so the point is moot, but it attracted $180$ downvotes before closure, so evidently this kind of thought process does happen rather often on the site.
The case against this sort of thing, as I see it:
The help page says "voting down a post signals [...] that the post contains wrong information, is poorly researched, or fails to communicate information". If a post does not have any of these flaws, it should not be downvoted. Your votes should be a function of the merit of a post, and not a tug-of-war against other users' enjoyment of it.
The case for:
Math StackExchange should serve as a lasting resource for many future users to view posts relevant to their interests. If you are willing to spend a few reputation points of your own in order to improve the relative position of relevant questions and answers, thereby making the site a slightly better experience for everyone, this is a valuable service to provide and should be encouraged. Post scores should be a function of their merit, not of their view count.
What is the community opinion on such behavior? Is this sort of action acceptable? Should it be accompanied by an explanation, if so?