Doubts, sure. Asking for more evidence isn't a problem. But 1) blaming the author and 2) insulting him with something baseless like "I found the article to be really naive in a Dale Carnegie kind of way, that probably appeals to someone in their mid-20s trying to reinvent themselves, but is actually a psychological dead end" is a problem and needlessly adversarial.
Given that, I think it's appropriate to raise doubts about its clinical effectiveness.