alt Hacker NewsPlenty disagreements everywhere. Under (usually fake) ideas of not enough resources for everyone, so the strongest must survive.
Nazi planned to exterminate several whole ethnicities. If you think it was (or is) unversally accepted as "Bad" -- think again. Most developed countries had Nazi parties, including US and Canada. Some sympathize today. Several Middle East governments publicly claim that murders/rapes/kidnappings of people from another particular country is just and honorable, and will be rewarded in heavens.
Ancient Spartans (reportedly) killed their own weak children. In order to become a citizen every Spartan must have killed a man (non-citizen). It was considered good and just (by citizens).
In many cultures tribal warfare was paramount, even before states (and some remote tribes practice it even today). It was considered good and just.
And we honor our veterans, and for a good reason. (Without them, we would be captured/killed by other veterans, and honor them anyway). Modern civilizational culture is a thin patina on top of our primal behavior.
I was thinking about your last point about why we honor veterans. In the US it’s not really the case that without them we’d be captured or killed. All our conflicts in the last several generations have been us invading or fighting in foreign lands against forces that were not attacking us. All our modern military personnel are willfully employed and well compensated and given lifetime benefits for that.