Watts doesn't deny the differences between those affected by ADHD and those who are not. He argues that these differences are best understood as personality traits and not products of an affliction.
This isn't a matter of ignorance, but interpretation of and reaction to scientific discoveries.
It's not a personality trait that I cannot physically do something I want to do and need to do without medication and, frankly, I'm sick of people who don't experience it offering new theories on it as if they have some grand insight into it.
Get a head injury that breaks your executive functions. Join us. Then try to offer it up as a personality trait.