Check out this article about Yoga. I have known folks who have totaken three to six months teacher training course in Yoga and then start teaching. People have to take responsibility for their health. If you want to do yoga, go to someone who is qualified and have taught it for years not some half-bake newbie who has no idea about the harm a bad pose can cause or no idea about the structure of the human body.
People have to start using their common sense.