Could it be that because of the medication, the symptoms weren't obvious enough for the new psychiatrist to see, thereby leading him to a false conclusion?
I would say that it could be a good thing to meet several psychiatrists if you're in doubt about your diagnosis. They all have different experiences in different areas, and some might not get you at all, while some will.
But if you think that your diagnosis makes sense, then I wouldn't bother listening to someone trying to prove you wrong. Experienced in psychiatry or not, they still don't know you better than you do.
Personally, I had to change psychiatrists because as soon as I told my first one that I suspected I might be on the spectrum, he just told me that "No, you're definitely not. Do you know how rare that is in girls? What you DO have is a personality disorder that looks a lot like AS, but it's not. Here, take this anxiety medication."
At first I believed him, but after a few meetings it became clear that he wasn't even listening to what I was saying. Kept telling me all about how my parents have messed me up, even though I barely said anything about them.
My current Psychiatrist was really great about it. I didn't want to say too much about AS when I first met him, because of my experience with the first guy. But as soon as it was mentioned (it's all over my journals) he was like "Oh yeah! That makes a lot of sense. Let's go ahead and look more into that."
Changed my life.
Some people have just made up their mind, and if you notice that someone's opinion of you isn't right, then screw them. There are better alternatives.