From the Preface:
All devils are liars.
Using the assumption that liars include or omit facts to create a half truth or falsehoods so the audience does not apply critical or rational thinking to validate the narrative.
The liar doesn't want you to think, simply accept what has been presented to you.
Knowing the author (or speaker) is a liar, even if you agree with what is presented, it is suspect! There is a motive and agenda, use that wonderful brain to trust but verify.
From the Christian viewpoint, can we verify that Satan and his minions lie?
I point to Christ's temptation by Satan and how Satan twisted and perverted scripture. More simply put, taking bits and pieces out of the Bible and out of context to drive a narrative.
Screwtape also alludes to using similar tactics when he reminds Wormwood of the older brother in the story of the prodigal. Take those feelings and reinforce with resentment. The minions have a real opportunity because the older brothers and sisters hopefully don't have a relationship with God.