AnnOMaly....You're exactly right. It's all based on Hislop, for the Society wants to claim that "false religion" spread all over the world when the people were scattered from Babel, and so Nimrod would be the guy who set it in motion. The belief that "false religion" started in Babylon is moreover pursued because it supports the Society's identification of "Babylon the Great" as "the world empire of false religion". Hislop thus provides what the Society thinks is independent proof that false religion got its start in Babylon.
Being uncritical about Hislop's credibility, the Society has for decades cited Hislop as dogma...Hislop's extrabiblical claim that Nimrod's wife was Semiramis was presented as just as true as anything the Bible itself said about Nimrod. As Woodrow points out, Hislop's scholarship is woefully lacking. One day I'd like to write about it in detail. One thing he does not mention is Hislop's imaginative pseudo-etymologies which reveal an utter lack of knowledge of Hebrew and other ancient languages. Hislop's ignorance of actual Canaanite and Babylonian mythology is also evident in spades to anyone knowledgable of these subjects. I have noticed that the Society in recent years has relied on Hislop much less than they used to and I wonder if this reflects some knowledge of Hislop's unreliability.