I can relate and find it very hard to deal with. It upsets me when people are so rude and belittling.
I have one friend who does the passive aggressive 'you miss out on so much' said with a subtext of 'its all in your head and you are making this up'. If I try to talk to her about it all she just changes the subject or pretends not to hear. I have tried to stick with it and not let it affect me but after reading this thread I realise that I am quite upset about it and will not eat with her anymore.
Yes, I have experienced the eye roll, the doubtful looks and some direct challenges.
I find that most of my friends now are either gluten-free or have their own food intolerances or other health issues. Those who have experienced the pain of being different are a lot more compassionate than those who have not.