>Languages should stand or fall on their own technical merits.

A nice sentiment, but not reflected in reality. It's valuable to evangelise languages because

  1. better awareness of their novel features can pressure more widely-used languages to adopt those features - like the addition of lambdas to Java, Python, etc. 
  2. otherwise you risk being stuck with whatever people know, forever. "Lack of fluency" is a technical demerit from the perspective of a project lead.