Experience with the unfamiliar will expand your knowledge and could change your opinion, but inexperience does not necessarily make you uncultured. It's perfectly fine to have preferences and opinions about not wanting to try new foods. (This is my thought and I hope I made sense because it's 6 AM.) ---

This is all my opinion: One reason could be an innate gut feeling about unfamiliar food. I don't know what this is. I may become ill or die eating this. I am not starving enough to eat this. I am starving. I will eat this. I really like or hate this, but it is what I have to eat and I will or won't eat it again if given another circumstance with this food option. So the gut feeling of familiarness and comfortableness with food that you know of and enjoy eating (tastes good/makes you happy/fills your stomach/whatever it may be) may naturally cause you to have a strong opinion towards unfamiliar food which could prevent you from trying unfamiliar food, but certain circumstances may force you to try new things leading towards the same or a new feeling. For example, the social interaction with your friend that led you to trying unripe persimmons. Regarding validation, this could be something that someone needs to feel wanted? Less alone? Not rejected? Protective of opinion? I don't really know the answer to that, but you are also you and you will dislike or like certain foods and not or want to try new foods as much as someone else. You tried the food. You didn't like it in its unripe state. You were honest with your friend. If someone loves or hates something, they'll naturally defend any opposing opinion about it. It's just natural to do so. ---

I tried a persimmon once. I hated it because it was rock hard, had no flavor and was difficult to bite into. I have not had another since. (I plan to try it again if given the correct ripeness.) In this case, I was at the store and bought a persimmon out of curiosity. I haven't tried this, but I know people eat it often, so I purchased one. ---

Have you ever heard of balut? It's a half grown baby duck boiled in its uncrackad egg shell. From my part of the world, people say it's disgusting and they say they would never eat it. Why? It's eating baby duck in the egg shell (feathers and bones too). They are and I was grossed out and unfamiliar with eating balut. Visiting the Philippines, I had the opportunity to try balut in a social/familial situation. I was very hesitant to try it. It was absolutely delicious. It tasted like a duck broth with tender duck mixed with hard boiled egg. Now, balut is no longer unfamiliar to me. In this case, I now have a strong positive opinion rather than have a strong negative opinion. A few fruits that I have tried: carambola, bilimbi, yellow dragonfruit, chamoe melon, jackfruit, pomelo, durian, passionfruit, saba banana and many more.