Authentic: genuine, real, not fake...so if someone sings an E. trad, e.g., with a phoney-American accent, another may say that's not authentic! Or just shout - yeehaa!
And, regards being on the TV, there we do agree - it's often stated that folk-rockers, Steel Eye Span, brought many into folk music (although, again, I'd much rather hear Maddy Prior's AUTHENTIC unaccompanied English folk-singing).