Why don't you just tell them that you're pretty well-versed? Doctors are pretty smart. I wouldn't presume to say this is always appropriate, but depending on the rapport they might listen attentively to what you know from your own research (though they would probably check before acting on it.)
Doctors know very well that a person with a specific rare disease has a lot more incentive to have spent in-depth research on it than they did when they last ran across it...
I mean, these days there are whole forums dedicatd to a specific disease. If you told the doctor, "You know, I ran across a forum for people like me, a lot of people have said they had very bad results with (x) despite the clinical trials, so I would prefer (y)"...you don't think they would listen to you?
Where is this attitude coming from?