Who wants to tell him?

What type of extremist content do they post?

Science is gatekeeping my imagination.

Gonna have to disagree with this. Not having a diagnosis gives people the false impression that ADHD is a state of being, a minor hindrance like having an “off day.” It makes it seem less distinct and thus taken less seriously. When that happens and someone seeks an accommodation at work or school they are much less likely to be taken seriously — which inhibits their ability to function in society.

Taking any prescription medication for a condition you do not have is fucking stupid and/or dangerous.

TLDR: Self-diagnosing is foolish and misinformation harms people that truly require equitable accommodations.