I am not an OO fanatic but OO is extremely useful for juggling a bunch of information in the best bad way possible. And juggling information in that best bad way possible is a way different problem from functional programming paradigm of finding perfect, elegant solutions to well defined problems.

What's the difference between:

    data Foo = Foo { a :: String, b :: String }
    doSomething :: Foo -> String
    doSomething foo = a foo ++ b foo

and

   class Foo {
       String a;
       String b;

       String doSomething(){
           return self.a ++ self.b;
       }
   }

If there's some deep fundamental difference between functional programming and OOP, it's not this.