I actually gasped when I read your post. Good grief - what an idiot!
Ask him if he knows what the internet is. Then tell him about this marvellous new fangled device known as a 'search engine'. He may have heard of the mythical 'Google'. Tell him to type in 'Rheumatoid Arthritis'. Or possibly, 'NHS Direct Rheumatoid Arthritis' It may just give him some answers as to how much it is in your head.

Sorry, sorry. I cannot cope with how ridiculous some people are! I'm exasperated in just hearing about him over the internet!
I can understand he doesn't get it. But seriously. In today's world of instantly accessible information - is it hard to find out?
*gently hugs you for having to put up with such a twit.*
Perhaps a general message to those he's discussed his *ahem*
knowledge with to clarify a few things as well? Something along the lines of '... I know some of you haven't encountered my condition before, but just to give you some ideas of how rubbish it can be - try these links...' followed by stuff from the NHS and NRAS. I suggest NHS first as they might be more inclined to try that, rather than an organisation some might feel has a biased opinion. Heck - even a wiki link might be good! Also the spoons theory page is always helpful in trying to get people to understand the whole fatigue thing.
I do hope some info might make him realise just what you are going through!
... And if anyone suggests it can be magically cured - add in that (according to Wiki) - "The first known traces of arthritis date back at least as far as 4500 BC." And how you wish someone had worked out what that cure was already because you'd be first in line!
*feels very blessed by how brilliant most of her friends are and how much they listen when she explains the basics and hopes that her sarcasm wasn't totally misunderstood over the internet*