Let me buck the academic norm again and say this. A master must know the primary sources. A teacher should know the primary sources. But, in terms of learning, secondary sources (including the teacher) are usually FAR, FAR, FAR more important than the primary ones. A good teacher or secondary source can abstract the key points in a relevant way, while primary sources are often obtuse and idiosyncratic.
The skill of abstracting information from a primary source is a useful one, and the deeper someone goes into a topic, the more important it becomes to evaluate secondary sources in the light of the primary ones. But when it comes to learning, the vast majority of students will learn FAR, FAR, FAR more--and FAR more students will be started on the journey to understanding--if you begin with summaries and secondary evaluations of primary writings, even if such summaries and evaluations would prove to be wrong on some details!!!
It is hard for me to express how frustrating I find the intellectual purist on these things. I can get the vast majority of college students in the door. Those who wish may then go on with the perfectionist to perfection, and they can laugh at how stupid I was on so many things. But the purist gets VERY few in the door with the "all or nothing" entry way, many of whom go on simply to perpetuate the same ineffective purism.
For example, I can see an honor's introductory philosophy class wading through some primary sources, but I GUARANTEE you that the vast majority of students in an introductory philosophy class will more be left with a disgust and distaste for philosophy--and a confirmed conviction of its general irrelevance--if you make them wade through the Republic or Marx's Communist Manifesto instead of summarizing and systematizing the key ideas of these thinkers from a contemporary standpoint.
So you tell me, O Academic Man, which is better, to get the 10 students who are able to follow you through the primary sources, or the 100 students I could lead to the same ultimate destination starting with secondary ones?
I have seen another evil under the sun, and it weighs heavily on me.