Yoga as Workout

As you probably know, I look forward to my Yoga workout once a week. (It's mainly Kripalu Yoga, if you're interested.) So I was curious to find out what the NYTimes book review had to say about some books on the history of Yoga.

Overall, it's very interesting, although I did take some umbrage to this mindset:

The image of incorrigibly individualist and materialist Americans rummaging through ancient cultures in search of eternal youth, beauty and self-gratification has long provoked scorn. “Yoga in Mayfair or Fifth Avenue,” Carl Jung sternly declared, “is a spiritual fake.” But such a fetish of the “authentic” assumes that people in the country of yoga’s origin have upheld a timeless and unchanging yoga rather than practicing what Wendy Doniger, the distinguished historian of Hinduism, calls the world’s greatest “have your rice cake and eat it” religion.

I've always been a bit puzzled by this "authentic" line of argument - the same arguement that tells they can't make any money from their music because to do so would be to "sell out" and jepordize their artistic integrity. In Yoga, what does it matter what a person's reasoning is for practicing? My intuition tells me that the mere fact that people are taking the time to be quiet, stretch their muscles and concentrate on their breathing will inevitably provide experience some spiritual benefits to that person regardless of their reasoning for practicing (typically for personal reasons - just getting into shape - or spiritual reasons - trying to open your third eye). Even if this is not the case, why the fuss?