Some things are believed because they are demonstrably true. But many other things are believed simply because they have been asserted repeatedly—and repetition has been accepted as a substitute for evidence.
When someone states as an axiom "all war is murder" or "war never achieves anything" and one asks how that applies to WW2, one isn't "appealing to WW2 analogies". One is determining whether they are a genuine pacifist (very rare) or a mealy-mouthed Nazi/terrorist sympathiser.