Strangely, I'm not really that invested in whether or not it was wrong not to kill Genocide.
But that's what you're arguing against.
The whole point of that plot was poking at Diana's moral foundation. She goes on and on about how she's going to kill Genocide, how Genocide needs to die. She questions herself, asks the very legitimate question "am I culpable in the deaths caused by Genocide because I failed to stop her creators when I had the chance." She wavers in her convictions, tries to suss out and re-assert what her convictions even are. And then she doesn't kill Genocide, and she's all ZOMG RELIEVED. It's a huge thing for her. She thanks her gods profusely that she didn't have it in her to kill. In this issue, with Phillipus, she goes on and on about how she couldn't kill Genocide, and Phillipus is like "yes, that's why you're cool and why we follow you." It is entirely about whether or not it was wrong to kill Genocide.
You can't write that story and then make it about Genocide being sympathetic (and you can't write that story and then cave in Ares' head). And you can't say "but I get why she didn't kill Genocide" in the face of that story and not be implicitly making a moral argument, because the question itself is explicitly presented as a moral choice.