I can understand how that is a hard situation if you don't want to offer any personal information. Just like you did, tell them you just don't like it. Depending on the people though I will just tell them something like I used up all my free passes already. It usually gets a laugh and they shut up. Only of course if you are comfortable with saying such a thing. I don't find my affliction something to be ashamed of, I am one of many people and have one affliction of many people. I don't let it faze me and it doesn't faze them.