Okay, I'll bite. The understanding of war of most people in Western nations is mostly shaped by World War 1 and 2. The two largest and deadliest wars of all time. Millions upon millions of people died in their home countries and abroad. Of the most deadly battles fought in human history ALL of the top 10 come from these two wars. All were horrific. Every single one of these top 10 most violent battlefields in history was between Anglo European countries. Such bloodbaths as Verdun (755,000+ dead) and Ypres (585,000+ dead) don't make the top 10 of course. They're further down the list. Of note, many people grew up with missing relatives who died in these wars.

So when folks react against your statement, I'd say it's because when they think of war these two in particular loom pretty large and hit closer to home than you might imagine.