In my opinion backing files (Of any type) are fine for live playing in concert providing the following rules are applied.
1. The files have been performed and recorded by the Artist themselves
2. The Artist plays all the parts that are physically possible to play, with the backing file used only to make the sound performance more real (Playing a Classical Orchestral piece is an example, as nobody has enough hands and feet to play all the parts)
3. The Artist does not make the audience believe that everything is played live.
In other words use them to enhance your performance, not as a crutch

Bill