Well, Ayn Rand was ethnically Jewish, and despised Christianity (which may have been a more common point of view from Jewish people back then). So she would have been skeptical of any organized religion that wasn't based on ethnicity, and thought people who chose their religion were foolish to practice such beliefs
If that's true she's an even more revolting human being than I previously thought before. "Ethnic religion" is one of the most disgusting concepts accepted in today's world.
That whole paragraph seems to be 100% supposition by Milhouse, and largely nonsense.