And if you're working in a hybrid language, what assurances do you have, really, that your system is really thread safe? Indeed, the risk compentation effect might give you a false sense of security, giving you a system that actually had more concurrency problems that one written in a "dangerous" language.

The phrase "hybrid language" in the original text is a hyperlink to Scala. By author's own admission, the languages he has tried were Erlang and Haskell. He hasn't mentioned either trying or not trying Scala, but the article seems to imply the latter.

The problem with what he said is that he seems to be dismissing "hybrid" languages like Scala as equally overrated or worse than pure functional languages like Haskell. Just like Jerf pointed out, it's the paradigm that matters more than the language. A language like Scala is designed to make FP paradigm easy to do, without being a pure functional language. As far as I know, it's not designed to make your programs "thread safe". I believe that the author wouldn't have made his claim about "risk compensation" if he had actually studied Scala and tried it out.