As a teacher (a female one at that) I have a few things to respond to...first of all, until you have worked with young children (I work in an elementary school) and have seen what a kid who REALLY does suffer from ADD/ADHD is like on and off medication you will never grasp the realm of what goes on with these little ones in their day to day life.
Two, I think it is definitely something that is highly overdiagnosed. Gosh, if you saw the test these kids had to go through you would be diagnosed as ADD/ADHD as well. But, there are a % of children and adults who truly suffer and need some sort of medication, change in diet, etc.
And third, I'd like to know who your uncle works with when he says that it is mostly women who can't deal with behavior issues. The majority of woman I have worked with do a superb job with classroom management (and I, myself, get the large % of "behavior issues" because I have always done so well with these children and they respond well to me). It may not be that your uncle doesn't have issues with these kids because he's a man, it could be a personality conflict or that he is someone who lets a lot of things slide. Many possibilities.
I can count on one hand the number of students I have truly thought are ADD/ADHD in my 7 years of teaching. You can't just send them to the nurse and get some sort of quick fix, there is quite the behavioral screening process and paperwork, testing, etc. that needs to be done.
A bit long winded I know, but something I had to get off my chest....