I have been saying similar things to clients for years and have been meaning to write an article like this. Especially about the dangers of shoulder and headstands, which routinely cause neck and shoulder injuries. Also, if the many yoga teachers I have as clients are indication, excessive backbending can be ruthless on the spine and SI joint.
Does this mean quitting yoga altogether? No, it doesn't have to, but yoga should be done without the hardcore push through the pain mentality of current trends and needs to be balanced with other forms of exercise. The average yoga teacher should have far more training into teaching and seeing proper body alignment than what I've experienced as a student (I had a yoga teacher tell me last week to straighten my elbows more in class while being totally unaware of his own grossly hyperextended elbows as he was demonstrating the pose). And certain poses really should be gotten rid of entirely (I will never again do shoulder stand and head stand for instance).