Arrrgghhhh! I know what you mean!! I was actually thinking of making a post exactly like this the other day.
My sister blames my drinking too much orange juice as a kid, my parents think it's my current diet that's making me sick, and it's always "you should eat this, you should not eat that, blah blah blah" and I just want to scream "Listen, I'm the one that's been dealing with this first hand for 10 years, I think I know what I can and can't eat"
The worst part is... My 15 year old cousin was just recently diagnosed with Crohn's disease. But it was a mild case and she's in remission and only on probiotics and vitamins. So after talking to my aunt about it, my mom comes home and tells me that my cousin's doctor told her that pizza is VERY bad for her because of something in the dough, and that she should NEVER eat chicken. So my mom's telling me now I need to take these vitamins and stop eating pizza and chicken completely, and that I'll get better.
I was so frustrated listening to her, especially when she was saying the doctor said IBS turns into UC which turns into Crohn's, and I tried to explain that UC and Crohn's are not the same, and it's different for every single person so just because she can't eat chicken doesn't mean I can't, and also IBS is a completely different thing and not even remotely related and that the doctor sounds like an idiot, but since my cousin is "all better", he MUST know what he's talking about. Grrr.
So I said screw it, went home and ate a chicken sandwich and went to bed. LOL.