He wants to learn RoR because he wants to learn "a new language" but by the sounds of it he isn't too psyched about learning a whole new web framework. I don't blame him, once you have seen one MVC framework..

So, why not just learn ruby but learn it in a context that has nothing to do with web frameworks? For example a program that can play music, a terminal script that automates something or a program to procedurally draw fractals.

You will learn ruby quicker because you won't have to get bogged down in details about how rails decides to do things.

If you find that you like the language more than what you are used to and wish you could write your webapps in this language you now have a solid reason to learn rails.