Applying the principle of charity to people you know but not to foreigners is a well-known failure mode that produced Soviet atrocities against Germans, to use Lewis' own example. And again, here is Lewis applying the principle of charity to a transformation-happy Sith Lord with a mind-altering book after writing these allegedly helpful quotes. He seems to genuinely not see the parallels between borderline-self-insert Coriakin and his most famous villain.

Lewis is explicitly writing religious propaganda. It's not coincidence that his advice would have his mostly-Christian readers focus on charity to Christian authority figures before Soviets, or even Church critics they don't personally know.