tl;dr:Armin observes two forms of pessimism - a “pragmatic form” and what he’s coined as “destructive pessimism,” which he believes has become more common inside and outside of engineering. Pragmatic pessimism can be useful - you assume that things are more difficult than they actually are and are able to highlight pitfalls along the way. Destructive pessimism wants, or expects, things to fail. While both seem similar on the surface, the latter can be harmful.
tl;dr:Armin wants a post-mortem on how the transition to Python 3 has been handled. There's a lack of transparency as to why the transition is needed. He feels like he's being "sold" and forced into migrating when, in fact, there are other reasons this migration is needed.