Perhaps you can argue an average person might come to that conclusion, or Jews might come to that conclusion, but I don't think it's reasonable to assert or believe in mass events based on secondary sources. The standards I have for myself I would say everyone should have.Therefore my accusation stands. A reasonable person at Nuremberg who believes in the jews in gas chambers story has every reason if not more reasons, to believe the jews into soap story. The fact that you are arguing they have no reasons to believe this, is a feature of narrative drift across time.
BTW I'm not saying definitively No Jews were soaped, just that there's no evidence of this, so that belief is unjustifiable.