I hate diarrhea, and not just because I relate it to vomiting. I honestly wlll know why I have it and know I won't be sick, but still panic. I actually hate pooping period. It causes me awful anxiety and I have no idea why. To most people it's a relief, I feel worse for a good hour after I have BM.
I spent most of my life constipated, and secretly liked it. Now I am regular due to my extra healthy diet, and even my normal BM's freak me out.
I wouldn't say I have a phobia, because it's not nearly as bad as my fear of vomiting, but it causes me almost daily anxiety for sure.