I ordered gluten-free sushi and asked additional questions (because I got hit the time before after many previous good experiences) and found out the staff was frustrated by people requesting gluten-free (and staff going through the menu, etcetera) and then ordering glutinous items. Yeah, frustration. We talked a bit and my waiter was happy to explain to the chefs that I was serious, and I got a safe meal.
Actually, a good friend of mine is a server at a high end French restaurant and this was a huge issue for him. He had several customers send him running back and forth to the kitchen several times to check ingredients, only to go ahead and order something with gluten in the end. I explained to him that those people were probably not true Celiacs and that I would never, ever order something with gluten in it on purpose. People like that make the real Celiacs look bad.
A couple of weeks ago he had a true Celiac come into the restaurant and he was able to help her order something safe. He told me about it the next day. Made me feel better that my "education" helped. I have started telling servers that gluten will make me very sick just to clarify to them that that it's not a fad for me.
As for the hostility of others, I sometimes wonder if it is because they know they need to change their diet but don't want to, so they become resentful of those of us who do.