Editorial: It is clear that what is called “health education” is usually propaganda rather than education.
Conclusion (It is clear that)
"Health education" is usually propaganda rather than education.
Evidence
Propaganda and education are never the same thing.
Propaganda is nothing but an attempt to influence behavior through the repetition of simplistic slogans.
Evaluate
Since we were given a definition of propaganda (nothing but an attempt to influence behavior through repetition of simplistic slogans), if we're trying to prove that,
Health education is usually propaganda
then we need to know that
Health education is usually [nothing but an attempt to influence behavior through repetition of simplistic slogans].
We don't have to worry about education, since we are told that it is never the same thing as propaganda. We also don't have to worry about the fact that propaganda is much more successful than education, because our only job here is to prove that "health education" is usually propaganda (whether it's successful or not).
Goal
Since the question stem already cues up the first few words of what we're looking for, we just need the backend. Health education is usually nothing but an attempt to influence behavior through the repetition of simplistic slogans.