My reason for saying that they are incapable of discerning good from evil comes from the fact that basically all of Europe and a large portion of America has declared God to be dead.
The Bible says "The fear of God is the begining of wisdom". Having rejected God, these people are left to flounder and flail about, grasping at what, to the human mind, appears to be reasonable and "fair." The rejection of God does not mean that one then believes in nothing; as a matter of fact, the rejection of God leaves a vacuum into which all manner of deception and "damnable heresies" then falls. The person who has no knowledge and fear of God has no hope of being able to know the difference between good and evil. There is no absolute truth; everything is relative and open to discussion and moral equivalence.
People who have turned against absolute truth will then believe anything. The people like the one who wrote this letter have made the choice to reject the only true Source of absolute truth in the universe and therefore have chosen to leave themselves open to the opposite of truth which is, of course, deception and untruth.
This is what we are seeing during the course of this conflict. The only good thing to come out of this is the stark desolation we see from those who don't know God and as a result live in a world of confusion, with no moral compass, no concrete moral foundation, and no One to Whom to turn for comfort in the midst of terrible circumstances.
Absolutely correct. They have abandoned God, and just as the Bible says, God has given them up to their reprobate minds. So they are left to their own devices, completely clueless and in the dark. In such a state, they fall prey very easily to every lie Satan whispers in their ears.