At the end of Harry Potter and the Goblet of Fire, we see the Minister of Magic so stunned by the idea of Voldemort's return that he can't bring himself to believe it.
"You-know who ... returned? Preposterous... you - you can't
seriously believe that. ... It seems to me that you are all
determined to start a panic that will destabalize everything we have worked
for...."
In later books we see him even more unable to consider Voldemort's return, unable to bring himself to face the facts, because of what it would mean.
Ultimately, of course, the facts became clear, and the wizarding world had to fight against Voldemort without the benefit of an earlier start.
It seems to me that the same thing is happening now, in much of the Western world, regarding Arab terror. Acknowledging the reality of Arab terrorists that kill out of hatred, not for a goal that we can understand but simply out of hatred, is too hard for people to handle. Like the Minister of Magic, people need to find something else to believe, anything else to believe, rather than face the fear of Arab terror.
Like "Cedric Diggory's death was an accident!" we hear "All they want is land for a state," ignoring that when given land they chose terror over building a state. Like "Barty Crouch was just a lunatic," we hear "They're mad at Israel for putting them in refugee camps," ignoring the fact that Egypt and Jordan put the Palestinians into refugee camps, not Israel. Like "Harry's making it all up!" we hear that the Palestinians only want a state on the West Bank and Gaza, forgetting that they said no to exactly that at Camp David ten years ago.
Like the Minister of Magic, the world will wake up eventually to the fact that responsibility for terror must be on the terrorists, and that the civilized world cannot excuse terror as a valid means to an end. And like the end of Deathly Hallows, we'll eventually reach a point where evil is destroyed and peace can spread.
Hopefully it won't take seven books for us to get to that point.