St Peter tells us, "Brethren, be sober an alert, for your adversary, the Devil, is prowling about like I lion, seeking whom he may devour." This is proclaimed as part of the First Reading on the Feast of St Mark (Ordinary Form).
Now, some of our separated brethren (or those who should admit they are separated) have taken to preaching that there is no Devil. They say that the Devil and Hell are all part of some out-dated theology. Essentially, they have bought into the modernist argument that proposes that, as Marx put it, "religion is the opiate of the masses." They don't go so far (usually) as to say that there is no God, but they do propose half of the argument, that Hell and the Devil were teachings used to manipulate the masses. Now, they say, we are more sophisticated. What they don't realize is that they are, in fact, sophomoric, literally, smart idiots. They are imbued with more knowledge from technology and other things, but they are too arrogant to realize how much they still don't know.
As for those who should admit that they are separated, there is no worse arrogance than to remain in the Church, with a collar or habit on (or lapel pin, as is usually the case) and teach contrary to the constant teaching of the Church. Instead of admitting that they are not in line with the Church and going to another ecclesial community, they stay within the fold as wolves dressed in shepherd's clothing. They love to tell people that the Holy Spirit is powerful in their lives, especially rich widows. They love to tell people that those teachings which might make them uncomfortable are optional or passe, and the people of God love them because, as the Apostle tells us, their ears are itching to hear false doctrines.
You'll hear it said, "Father Russ is a really great confessor," meaning, "Father Russ tells me that I'm great; I don't have sins, only human imperfections." They don't like going to People Like Us because we tell them that to embrace the Divine Mercy means a change of their lives.
No one, however, has ever truly encountered Christ and been left the same. To encounter Him is to be transformed by Him. Then, and only then, can we fulfill what he promised in the Gospel of Mark -- "power of demons." Yes, Christ said "demons!"