If you don't think you would be able to fool the person that you have the same views as them, you probably will not be able to have a productive argument with them.
i.e. if you couldn't sit at the table with a bunch of (insert ideology) adherents and blend right in, you probably don't understand their views well enough to dissuade them from it.
Jonathan Haidt's finding from The Righteous Mind that conservatives tend to understand liberal moral foundations better than liberals understand conservative ones is an important example.
His research shows conservatives operate across a broader range of moral foundations—care, fairness, loyalty, authority, sanctity, and liberty—while liberals lean heavily on care and fairness
This gives conservatives an easier time modeling liberal views, as they already incorporate those priorities. Liberals, however, often struggle to grasp the weight conservatives place on loyalty, authority, or sanctity, seeing them as less "rational."
The author is an example of this: he views his opponents as less rational—literal "toddlers"—and thus their arguments can be dismissed.