He's wrong about climate change but this is such a shallow piece of rhetoric. He's a "guy" who is a respected research psychologist with lots of clinical experience. Out of anyone, this makes him more likely to have interesting things to talk about when it comes to self-help. At least far more than gurus. The fact that he suffers from chronic depression, which is largely a BIO-psycho-social (emphasis on bio) problem, is irrelevant and is a total low blow.

I could counter your argument and say that him pulling himself out of his recent depression is evidence that his ideas work. If a dermatologist gets an acne breakout and then fixes it, we don't blame them for the breakout, we commend them on addressing a difficult problem. Either way, this counter-argument of mine, and your original argument, are both silly. If his depression was more biologically grounded, he deserves neither credit nor blame. If his depression was due to social situations like cheating on his wife and feeling immense guilt, then yes, we can blame him for creating a depression based on his own stupidity. But neither of us knows the situation and so it's an irrelevant thing to bring up at best.