Would we knock Oklahoma because it isn't American folk music? Why knock Riverdance? Might as well knock Who Wants to Be A Millionaire or WWF wrestling - none of them are connected with folk music but if people like them- great. Why get bent out of shape?
I've seen Riverdance, it is a wonderful show and I had a good time. I also got a kick out of Star Wars. Neither one changed my life, but that is me. The media hyped both and lots of people received enjoyment - so what is wrong with that?
If people find their way into the world of trad and folk music because of Riverdance, that is wonderful. That is not the purpose of the show. Riverdance shouldn't be looked at as trad music or expected to be a representation of traditional Irish music.
Incidently, I have a wonderful album of trad music that Michael Flatley recorded in the early 80s. He is/was a decent flute player and has/had a respect for the tradition. I wonder why the album was never re-released with all the hype surrounding him in recent years. Too close to the source for comfort perhaps?