It's all about thinking frameworks. Ensuring that effects are declared, that data has a static lifetime, or that your program is rewritable data are tools you can use to focus your mind in one part of the problem and less in another. Just like having irestricted access to everything your computer can do, or data + code encapsulation with multiple access levels.

Not recognizing this (like in the article) is a clear sign of a single-paradigm developer that never really understood anything else but is too arrogant (insecure maybe?) to assume he doesn't understand something. So, the problem must be with everybody else.

Anyway, a funny red-flag is that reaction to Haskell IO. People that never really learned Haskell tend to complain about IO with a deeper complaint of "why to I have to keep using monads?", while after people learn it they tend to complain about the lack of monad composition, with a deeper complaint of "why can't I use monads for everything?"