I agree that any serious programmer should be able to be productive in any language, but mastery of a style of programming takes time. It's easy to move about

I agree that any serious programmer should be able to be productive in any language, but mastery of a style of programming takes time. It's easy to move about in the same style of programming, but trying to move someone from enterprise-y OO (Java, C#) to functional (Haskell, Lisp) or even Go is a bit of a leap. Concepts often just don't cross over. A Go channel, for example, makes sense to an Erlang developer, but not a Java developer. Goroutines don't make sense to someone familiar with traditional threads. There's a certain amount of rewiring that needs to be done. Looking for a "[language] programmer" is strange, but looking for someone proficient in the style of programming used makes sense to me.