Please consider that Japan, USA, EU, Britain and Canada all have different music copyright and fair use policies, MMOs have been sued over play created content, and that streams and recordings of FFXIV gameplay are automatically licensed to SE.

Fair use protects you from the music giants but will not protect SE as technically you are not playing a cover song, you are directing SE's servers to play a song that they may not own nor have the license to reproduce. This is what SE's legal team is worried about.