Something has occurred to me which makes me think we may be talking about different definitions of 'teaching'.  My experience is with students in grades 5 through 12.  You seem to be discussing teachers in a college setting.   Very often, college professors have never been through teacher training, or worked as a certified teacher, they just attended university until they had a doctorate and then were hired as a professor, where they proceeded to present their theories (sometimes strange) and publish papers.  They are not necessarily 'experts' on anything, but expect to say things in their own way, for students to sort out.  Such a setup makes it even more important that students learn to tell truth from nonsense in high school, before they are exposed to radical ideas.