You aren't going to understand the genetic causes of behavioral issues when the trait is highly polygenic unless your head is full of well-validated notions from genetics. So you're basically saying that Gabor Mate is ill-equipped to understand what he's talking about.

I'm all for gaining what knowledge we can from astute, thoughtful observation. But the idea that a huge body of work, much of it rigorously done and carefully verified, documenting the genetic heritability of a condition, can be discarded because of one person no matter how brilliant who "observes and thinks" is, well, preposterous.