It strikes me that many of the dislikes on this thread are more to do with texture than taste.
I tried an oyster on holiday a couple of years ago. It was deep fried in batter as part of a mixed fish dish. I really didn't like the taste. It was a fishy sea taste.
I like most things and will try most foods, but I draw the line at snails. I dislike winkles and whelks and as I have heard that snails are similar texture-wise I will give it a miss.
I admit that I do judge some of the "I don't like any Chinese or any Italian food" posts. These cuisines cover a whole spectrum of dish types that I struggle to believe that there is something they couldn't find to eat.
The food item I loathe the most is parsnips. I don't like beetroot or artichoke much but will eat them if hungry, but parsnips are utterly loathsome to me. I have tried tripe and disliked it, but am OK with liver and kidney.
I haven't yet come across a food that would make me heave, but I don't think I would like to try fermented shark (an Icelandic speciality) or the fermented fish they eat in Norway.
Heaving at everyday foods is an extreme reaction though, and I would wonder if that person had an eating disorder.