"There's nothing so absurd that if you repeat it often enough, people will believe it." ~ William James
The Law of Many Devils
There are many things that bedevil humanity. Ninety percent of them are located in human nature. If there is "evil" in the world, it comes right out of the human heart.
To say that people are "imperfect," or if you want to use religious terms, "fallen," isn't enough. What's wrong with people has to be analyzed, so it can be studied.
In my view, one of the main things wrong with people is their inborn tendency to split things into either Good or Bad, with nothing in-between. I consider this to be a law of human nature, one that researchers believe starts in us as infants.
That splitting into either Good or Bad (with "us" as good and "them" as bad) leads to scapegoating. If we consider ourselves good, then our denied badness has to be projected elsewhere, onto other people. Sometimes those scapegoated have done bad things. That's not the point, though. The problem is the splitting into Pure Good or Pure Bad, which automatically leads to scapegoating.
A person who does this splitting will never be able to see the truth. "They attacked us because we are good" is a perfect example. It ignores, "Maybe they attacked us because we've been attacking and abusing them for the last 50 years."
That splitting into Good or Bad, with the attendant scapegoating, next leads to Hubris, or what the Bible calls "pride." That's when you think you are human and your opponents are sub- or non-human. That's when people say, "My country right or wrong." They think it's patriotism, but it's really idolatry. We god-like; you're an insect that needs to be squashed.
Next comes seeing Bad as Good. The Greeks called that Ate, which they considered madness. Some examples of that are saying, "We'll kill them until they give up" or "Too bad innocent children and babies die in war, but that's the way it goes. Can't make an omelet without breaking a few eggs." Of course, what they invariably mean as long as it's someone else's children, but never theirs. To murder other's children for a "good cause" is acceptable, but their children being murdered is always bad. The Greeks were right about Ate.
What we have, then, are the Four Laws of Horror: splitting into Good or Bad, scapegoating, Hubris, and the seeing Bad as Good.
I have read a fair amount of horror fiction. Like all fiction, it's just an expression of human nature. Since horror fiction exists, it means there is horror in human nature.
All horror fiction is about good versus evil. Specifically, it's about evil attacking good, because whatever is evil--whether it oozes, crawls or bursts through from some other dimension--wants to conquer/eat/destroy the good.
The first thing that all horror fiction does is split things into Good or Bad. If it didn't, then there couldn't be any horror in the fiction. With that first split, whether in fiction or in people, there could not be any human-generated horror.
Without that split, there wouldn't be the belief in Good or Bad with nothing in-between, there wouldn't be any scapegoating, there wouldn't be any Hubris, and there wouldn't be that madness in which the Bad is not seen as Bad but instead defended as Good.
I mentioned all religions understand the imperfection of humanity. They understand where this imperfection is located: in human nature. They even understand that evil is due to what Russell Kirk called "the monstrous ego." Hubris, pride, the "ego," the "self" in the Eastern view.
Unfortunately, in the West, religion has often failed to understand the horror of that splitting things into Good or Evil, with nothing in-between. Sadly, sometimes religion even celebrates it, in the case of supporting the idols of State and country. That is why we get such monstrosities as the fraudulent Jerry Falwell claiming, "God is Pro-War."
Of course he means God is pro-Falwell's war. He is good, his opponents are evil. Being evil, it's okay to murder them. Clearly, when religion supports that false dichotomy between Pure Good and Pure Evil, scapegoating, hubris, and Ate, then religion becomes evil. And that is why, in my view, many legitimate religious teachers in the past have claimed many people couldn't tell the difference between God and the Devil.
Some people, seeing the damage that perverted religion has visited on the world, would like to see religion eradicated. It will never happen. I'd make the argument everything is religion, including secularism.
The first step toward fixing a problem is to analyze it and understand it. A problem can never be fixed if you don't know what the problem is. And until the religious understand that the perversion of religion isn't a minor problem, but a horror, the problem will never be fixed.