We know a covert fool understands the rudeness and deceit they are exerting because they hide it from those they wish to impress and are secretly blatantly rude to those they disrespect.
When someone hides their true nature from some and not others they are making the decision to do what they do whether that is to trick the ones they want to impress with a false image or to treat others they disrespect with contempt through intimidation and mocking.
The goal of the fool is to bring their target down fostering discontent and diminishing confidence. The hope is that the target will lose control out of frustration and return anger for anger. The smartest thing for the target to do is to remain calm, not answering a fool according to their own folly, and avoid the fool whenever possible.
When they realize they are not able to control the self-assured person they will gossip to others who will torment the hated one on behalf of the fool.
The fool makes the mistake of amping up their rudenss and engaging others to their own downfall. Eventually, those who have been used as flying monkeys to do the fool's bidding will realize they have been played and will remove themselves to avoid the drama.
Anyone who does not do the fool's bidding will be maligned too when they become aware and detach themselves.
Our world is becoming more foolish every day, rational thinking is no longer the norm but the exception. Our greatest hope and joy is to remain calm, seeking Christ for everything, and remain untouched by the devil's schemes. And, yes he has schemes every day all day long as he attempts to pit people against one another especially Christian against Christian.
1 Peter 5:7-9 "…7 Cast all your anxiety on Him, because He cares for you. 8 Be sober-minded and alert. Your adversary the devil prowls around like a roaring lion, seeking someone to devour. 9 Resist him, standing firm in your faith and in the knowledge that your brothers throughout the world are undergoing the same kinds of suffering.…"
James 4:7
"Submit yourselves, then, to God. Resist the devil, and he will flee from you."
We can know the schemes of the devil by reading the Word of God. It began in the Garden with Eve when the devil turned Eve against God defending her disobedience through the lying justification of the devil. We do not have to be deceived as Eve was, we have the Holy Spirit and plenty of examples in God's Word and in life experience to show us how this wicked serpent operates to be able to thwart his plan to ruin our character.