Yoga is a life practice and philosophy – not a religion (read an excerpt from Georg Feurstein’s “Deeper Dimensions of Yoga” – which I highly recommend). It is rooted as a path for spiritual enlightenment but it isn’t a religion. We are encouraged to find our truest selves, not as it is dictated by any person, group or cultural or religious expectation.
That this practice – whether we focus on the one limb of asana (physical postures) or any of the other seven limbs (i.e. breath control, meditation, the ethical dos and donts) – can come under attack by someone waving the banner of Christianity is unfortunate. Yoga practice can help enhance one’s spiritual connection in my experience.