If your biggest defense of a programming language is "it allows you to easily change a closure's captured variables" and "you can do good monkeypatching"... Maybe it's not such a good language.
P. S. Also they told me Ruby's monkeypatching was bad because you couldn't do it in a thread-safe way... That's when I realized I don't want to talk to them anymore.
P. P. S. And, and, as I recently realised, they’re wrong. In MRI (CRuby, “default” implementation) monkey patching is threadsafe because of GVL.