Some atheists can be. Most don't. We understand it's irrational - like being afraid of the dark.

Are you afraid of going to some other religion's version of hell? Do you lie awake at night worrying about whether you'll be reincarnated as a dung beetle? No? Why not? It's because you weren't raised to fear another religion's consequences.

"One man's religion is another person's belly-laugh" applies.

Similar to a childhood trauma, where one can have a fear of snakes, closed spaces, dogs, etc., many fears and biases that one grew up with can linger for the rest of a person's life. That doesn't make it real or legitimate. People can irrationally fear something. That's normal human behavior. Some can work past their fears, and many never have had them.