If I get confused, the general population must be confused?

The debatable leg extension or the crunches is my two main examples. These two exercise people have really been doing for years. In fact I knew some great athletes that these two exercise were part of their regular routine.

My point is everywhere you turn fitness professional seem to disagree with one another. What is the best exercise or which exercises to avoid, some say bad technique and other say it's okay?

How do we educate the general population without added to the confusion?