If you don't believe there's some organising principle, or somebody up in the sky pulling the strings, then it can be very stressful. And nature itself is very arbitrary - it's not malevolent or benevolent; it doesn't even know we're here.
Spiders - the way they move freaks me out. It's so malevolent.
For nobody is curious, who isn't malevolent.
Seeing my malevolent face in the mirror, my benevolent soul shrinks back.
The most blatant forms of denialism are rarely malevolent; they combine decency, a fear of change, and the misguided desire to do good - for our health, our families, and the world. That is why so many physicians dismiss the idea that a patient's race can, and often should, be used as a tool for better diagnoses and treatment.