What makes so many people deny the highly probable truth?

One night, you wake and hear raised voices in the apartment next door.
A “domestic disturbance”.
The next morning, you hear that the woman who lives next door was beaten up.
Nobody knows who did it.
But one thing YOU know is that it was probably a guy.
It so often is a guy in such cases, that it is reasonable to suspect that this time it is as well.
The next day, you hear that somebody tried to to set off a bomb on an airplane.
The authorities have a suspect.
You say to your friend “I bet it was a Muslim terrorist”.
Your friend accuses you of unfair racial and cultural bias.
“After all” your friend says, “Timothy McVey was not a Muslim, and he was a terrorist”
But let’s face it. Muslim terrorists love to blow up or crash airplanes because they think the West carries the seed of Satan.
McVey blew up a federal building because he hated the government.
Big difference.
So why are so many people reluctant to face the facts?
Airport security, pat downs, xray scanners and the like are all about Muslim bombers, not mental cripples like Timothy McVey.
And yet, the TSA, and lots of people on Fluther righteously insist that everybody on earth is likely to use an airplane as a vehicle for mass murder.
Even though history and intelligence say otherwise.
Why won’t people admit it?