Can fallen angels appear righteous?
The devil is the father of lies (John 8:44) and is constantly scheming on how to bring people into his demonic kingdom and keep them from salvation in Christ. One of the greatest ways he fools people is by using false religions. Many religious leaders have the appearance of goodness and kindness but are preaching false unbiblical doctrines. Inwardly they are ravenous wolves (Matthew 7:15).
"You are of your father the devil, and the desires of your father you want to do. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he speaks a lie, he speaks from his own resources, for he is a liar and the father of it" (John 8:44). P
"For such are false apostles, deceitful workers, transforming themselves into apostles of Christ. And no wonder! For Satan himself transforms himself into an angel of light. Therefore it is no great thing if his ministers also transform themselves into ministers of righteousness, whose end will be according to their works" (2 Corinthians 11:14-15).