There are a number of sites where discussion about the legal or ethical concerns around conduct in conflict and war are on-topic. Law and Philosophy come to mind. It could also come up in the context of History and Politics, as well. And, due to their cultural and philosophical nature, the religious sites such as Biblical Hermeneutics, Buddhism, Christianity, Hinduism, Islam, and Judaism (Mi Yodeya) could also contain these discussions.
Assuming that a question is asking something about the legal, philosophical, ethical, historical, political, or religious background for the treatment of civilians and it's being asked on a site where the underpinnings are on-topic, then I don't see how it can inherently violate the Code of Conduct.
And the key components of the Code of Conduct are advocating or encouraging violence. Explaining what the law says, what a specific philosophy or ethical system would say, a particular political entity's viewpoint, or what a specific religion's text or religious leaders say don't inherently advocate or encourage violence. Likewise, stating (ideally with appropriate citations) that a particular entity's laws, philosophy or ethical system, political entity, or religion say about other groups of people doesn't inherently demonize or denigrate them. Objectively, it's important to understand how others see people.
I fail to see how an answer that simply states that a particular religion doesn't find killing civilians unacceptable would be a violation of the Code of Conduct. However, context matters. If the poster added additional commentary that promotes, encourages, or glorifies harm, it could fall under the Sensitive Content and Imagery policy. If it celebrates violent actors, it could fall under the Harmful Political Content policy. If it spreads false and misleading information that could cause harm, then it could fall under the Misleading Information policy.
If you want to stay in the realm of generalities, then I can think of places where there very well could be discussions about the killing of civilians and those discussions would not be inherently against the Code of Conduct. I would even go so far as to say that prohibiting such discussions, in those contexts, would do more harm than good as it would not allow people to have high-quality, cited, peer-reviewed answers that present objective information about the views and perspective of others.