Rabbi shapiro explains that it’s similar to the laitzonei hador who claimed that sorah had conceived from avimelech. Why are they called laitzonei hador? Because how can a person think that Hashem wouldn’t do nissim for Avrohom, a tzadik, but would for avimelech, the rasha? He’s belittling Avrohom in saying so.
Ever wonder why the same people who consider themselves “rationalist”, eschew kabalah, doubt things like golems, mock chasidishe stories as folk tales, and seek to explain Torah in the most non-miraculous way possible.. suddenly become miracle loving fundamentalists? Tell a zionist you have doubts about krias yam suf, and you’ll have a listening, compassionate ear… Tell them you have doubts about if the wars were miracles, and you’re an enemy of the nation, a horrible descendent of the miraglim, etc