“…be a lighthouse to all souls who wander in the darkness of ignorance of God’s love. That you may shine all the brighter and draw all the more souls, do not permit the untruths which come out of your mouth to silence your conscience…”
If an untruth is allowed to be spoken long enough, it becomes truth, while real truth is rationalized away. Our Lady seems to be saying that many know they are speaking untruth today, being led by the spirit of the world, and the more they continue to do so, the greater the possibility that they will delude themselves and their conscience.