I like James Anderson's answer, but I want to look more closely at your interpretation of Zed Shaw's comments. I don't think Shaw is saying to be "neutral to languages". In fact, the only way one doesn't become "blinded" is to care enough to learn enough to form a positive or negative opinion so that you can choose the best "tool for doing interesting things."
Given that, in my estimation (as a long time developer and manager of such people) a good coder does care very deeply about tools used and not just the output, because he or she knows enough to be aware of what will work and what will not work for the situation at hand.
Looking at your writer analogy, "like writer does not care about pen he uses - he thinks about the BOOK content", I would actually make the analogy this way (although believe me, writers care about pens :) ) -- a writer wants to put forth a message, and the medium through which he or she does it could be a sonnet, a haiku, a novel, or a song (and so on).
A "pro developer" wants to put forth a solid architecture and an application that scales, that meets the needs of the stakeholders and so on -- he or she could do that with Ruby, Python, Java, whatever, and the decision about what is best hopefully comes from a person or team that has the ability and knowledge to take all the factors into consideration.
So, as to your question, "is it a sign of pro developer, if he does not care what language to use?" My answer is that a "pro developer" does care what language is used, has a well-formed opinion about it (as opposed to an answer like "use Ruby because all the cool kids are doing it"), and if needed can roll up their sleeves and do the work even if it means working in Java instead of Ruby (and so on).
However, remember that people who work in places where the language is dictated for them, and are quite good at what they do in that one language, are still very much "pro developers", but they might be less able to have lengthy discussions about suitability of language for task if they only know the one language. Doesn't make them less "pro", just that they wouldn't be the only people I would have in a room when I'm soliciting thoughts on languages to use for an upcoming application.