Possibly true, though I would question the quality of any lesson about Nazi propaganda that did not mention Goebbels' name. If you are doing the "3-lesson 10,000 foot overview" of the 1930s and 40s then I can see how Goebbels' would escape mention, but otherwise he is definitely in the top 10 figures to mention.

I don't know about you, but I tend to forget details that I don't regularly use. I have learned about Goebbels and forgotten his name at least once. I focus primarily on remembering the lessons learned because I know I am likely to forget details such as names. I can usually remember the overall lesson learned because it resonates with my intuition and world knowledge.

Not knowing the names of prominent figures is some (quite inconclusive) evidence of insufficient familiarity. Any encouragement of the type I was speaking of should recognize that (and should be polite on other counts as well, of course) or is not entirely appropriate.