I personally believe that there is no such thing as "stupid" in terms of fear or phobias.
I have a somewhat arachnophobia which means I 'm afraid to be near a spider, no matter how small it is. To some people it might be stupid or funny because I am obviously the bigger one. However my fear is my fear. I freak out whenever I see one.
I love your answer ,but I guess I meant an abnormal fear like mine. A fear that is. Not common....