I've been in your shoes, and there is nothing funny about it.
I had a neuropsych tell me that I should prepare my son for manual labor jobs because he would never have the mental capacity for some of the jobs my son said he was interested in like physicist, software engineer ... He said I shouldn't feed that in my son because it was setting him up for failure.
I didn't laugh it off. I had a not very pleasant conversation with the neuro about his comments and the damage they did to parents with twice exceptional children - and to the kids.
I had him retested through a psychologist who contracts with the school who has experience in testing kids with learning disabilities and gifted IQ's. He qualified for gifted despite severe learning disabilities that skewed the results. The tester said his IQ is obviously much higher than the score she got but since it was high enought to qualify him for the classes we needed, we decided to stop lab-ratting him.
I personally would write a letter questioning the validity of the results and asking for a full evaluation from a professional qualified to deal with learning disabilities AND gifted IQ. If you have the money and you can find a specialist who has this background, I'd be willing to pay for it.
Good luck. I know how you feel right now, and it isn't fun. But you are your son's best advocate, so hang in there and be tenacious.
