The moral high ground is absolutely critical in war. War is politics by other means, and being able to build consensus, marshal resources, recruit personnel, persuade allies to help, persuade adversaries to surrender or lay down their arms, persuade the allies of your adversaries not to get involved, and keep the peace after a war is over, all depend on one’s public image. There are ways to wage war without it, but most militaries that blatantly disregard morals find it difficult to actually win.
In this case? The entire military strategy of Ukraine in this war is highly dependent on preserving the moral high ground.
I understand and agree with your point, but the fact that people are worried over whether Ukraine is killing nicely enough is ridiculous to me. It’s a defensive war of survival. The moral high ground is already theirs.