It seems to me that, when people talk about functional programming, they're talking about two different things. There are languages with good functional programming support, like Python 3, Scala, and Rust. Then there are pure functional languages where mutable state does not exist outside of monads, like Haskell and (I think) Erlang. I'm pretty sure nuffkins was complaining about proponents of the latter.
Of course, in their defense, Erlang has been used to build practical things a bunch of times. It was born out of a desire to build telephone exchanges. So, you've got at least one functional programming language that people have used to solve real problems.
Pure functional languages still weird me out and I have no idea how to build anything in any of them. Take my opinion with a grain of salt, since I don't know shit.
Functional features in imperative languages are pretty sweet, though, in my experience.