In of itself, no, it is not bad. Bad code can be written in any language and any programming paradigm. That being said, I would encourage anyone interested in learning functional programming and functional programming languages to do so.
There are many languages such as F#, Erlang, Haskell, Elixir and Closure that encourage good functional programming practices.
Most modern general purpose languages have functional features. C#, JavaScript and Swift support immutability and higher order functions.