No, there is no such rule.
But that does not mean it is okay.
Neither is there a rule that says I cannot list every top user of the site, along with a personally tailored disparaging comment about their posts that is entirely factual and delivered without any explicitly offensive words. Technically speaking, such a post has no “subtle put-down” (it’s overt) nor “unfriendly language” (the language isn’t the problem, it’s the idea it’s being used to express); it’s not “name-calling” and not a “personal attack” if it truly focuses on the content and not the poster; and a single occurrence of this probably doesn’t rise to the level of “harassment”. And “be nice!” is no longer in the Code of Conduct. So hey, if I make such a post, I’m not breaking any rules so it must be ok, and the Moderators’ hands are tied. Right?
Yeah, not so much.
It’s been quite plainly stated by more than one person that the original form of your question, in its framing, is in very poor taste. It literally starts by telling the reader they must “either support Syrian Rebels or Assad, neutrality is NOT an option”, and goes on from there. This is a global site, and the conflicts your question uses as its central conceit are not distant hypotheticals for many of our visitors and members. If this causes them great personal discomfort, and they say so, it is no longer within the spirit (nor, frankly, the letter) of the rule that you “Be inclusive and respectful”. Just as your freedom to swing your fists ends where someone else’s nose begins, your freedom to control how your post is composed ends where it causes someone else harm.
Even in the absence of an explicit rule against them, some posts are not acceptable on this site. The issue here is not that a real-world political situation is implicated, but that real-world people are, and that despite them saying so, your campaign to return to the original wording continues to do them harm—this is not Being Respectful.
• But I didn’t choose to make this political, “I discovered this puzzle in a political video game”
I heard an amazingly offensive joke the other day, that was misogynistic and racist, and made a mockery of various other minority groups. If I post it and make a puzzle out of its punchline that should be fine, right? I mean after all I didn’t write it, I just adapted it a bit to post it here ...
Yeah, not so much.
It’s your post here. You are responsible for what it says. Profanity is generally not allowed on Stack Exchange sites except where the word(s) in question are the heart of the question. Similarly, while exceptions may be made for language or ideas that are very likely to be inimical to others, if such is indivisibly the core of the question, beyond that such expression should not be permissible (and will not be, on my watch).
Using someone else’s content isn’t a way to get around not being able to post something objectionable.
• “I act according to the golden rule here. There are things that trigger/bother me too, but I don't insist on censoring content that involves them ...”
First off, you probably shouldn’t use the word “trigger” here. People who are discomfited by your puzzle’s original form may very well be accurately triggered by it. Your usage of the term for a visceral reaction to slaughterhouse imagery tends to be dismissive of, and thus disrespectful to, people who have ongoing psychological impact from life-altering events in their past.
Having said that, nobody has a right to go through life without encountering anything they find personally objectionable, offensive, or harmful. I mean, there’s probably someone who will deeply disagree with or be offended by pretty much anything anyone says, ever. Since we can’t please all of the people all of the time, it’s fine to just discount any pushback as the inevitable complaints of minorities, amirite?
Yeah, not so much.
If it is really your intent to “act according to the golden rule” then it’s unclear why you would want to continue campaigning for something people are telling you is causing them harm. This is not a case where someone might hypothetically take offense to something you’ve said. This is people saying you are treating casually something that affects them on a deep personal level, and that this is actively causing them harm. That is antithetical to what the Golden Rule is about.
Not knowing someone else is actually harmed by something you’ve said might excuse saying it. It absolutely does not excuse insisting on repeating it, or preserving it. While “Be Nice!” is not written in so many words in the Code of Conduct, it’s the foundation on which the Code rests. Campaigning for something people are telling you is harmful is not Being Nice.
• “Because I'm stubborn. For my subjective taste the wording is OK because ...”
Anything subjective is my opinion vs theirs, and who’s to say whose position is “right”, right?
Yeah, not so much.
Even where rules don’t make something explicitly out of bounds, Community standards often do. And, beyond that, Moderators serve as the human “exception handlers” to help steer their users and their sites in the right direction, and they are elected because their community trusts them to do so with due diligence and care. And, should they overstep, the community can seek to correct any harm done.
So I’m going to state my opinion that the post, in its original form, unnecessarily uses subject matter that a reasonable person could or should know is likely to be divisive or harmful to others; that just because a position or an opinion is a minority one doesn’t mean it is okay to dismiss it (and, indeed, there are many cases where minority positions need to be actively defended lest they be unfairly lost simply by being drowned out); that there is good cause here to curtail the right to express oneself freely in the manner of one’s own choosing because it overly impinges on others for no benefit; and that in the face of rational and rationally expressed objection to the original post, leaving it in place (or restoring it) is not being respectful to those it harms and is thus discordant with our Code of Conduct.
At this point I am tending to agree with another commenter that it seems hard to imagine you persisting here in good faith.
I will be cleaning up some comments that are a bit too aggressive from both perspectives, both here and on the puzzle post itself. The edit wars have stopped, but if there is continued effort to restore the original form of the puzzle, I will take appropriate action to forestall that as well.
Sometimes, in the case of a disagreement of opinions, Moderators need to step in and act on their consciences. I am doing so.