In my experience, people like this spend all their time screwing around with esoteric languages and abstract debates about semicolons, and don't spend any time building anything of value anyway.
This isn't to say that you shouldn't learn Erlang, or Scala, or Haskell, or any number of oddball languages. Doing so makes you a better and more-rounded programmer. But the haughty attitude of 'Blub is better than Blarb' reeks of naïve fanboyism.
Every language brings something to the table, despite their drawbacks. Ruby is beautiful and a joy to work with. Python is powerful and has amazing libraries. PHP is easy to pick up and has a huge community.
Ignoring languages because they aren't 'purely functional', 'high performance', or 'mathematically correct' is hugely ignorant.