I have been phobic of crabs since early years - I think I was scared by one in the sea and I remember running screaming from the sea. Elder brother's teasing didn't help.
Not sure I was ever actually scared of them in the sense that I felt they could do me harm, it was more the horrible feeling I got when being surprised by one, or even a body part. Very odd.
However now over 40 years later I have become relatively desensitised and could handle a dead crab. possible even a small live one. I take a lot of pleasure in walking & jogging on beaches as long as I am wearing shoes, and even visit the sea occasionally as long as I am fully clothed in a wetsuit with boots - definitely something to do with standing on one in my bare feet then!
Incidentally it has only ever been the 'saucer shaped' crabs that give me the heeby-jeebies, hermit crabs don't have the same effect. Not too worried by spiders either, which are similar shapes.
Do I want 'treatment'? Not really, I am very sure that being locked in a room containing hundreds of the things or carrying one in my hand would be the stuff of nightmares until the day I died.