According to Jacques Ellul (the favorite author of the Unabomber, and one that, ironically, almost led to his arrest) it is education that makes us vulnerable to propaganda.

From the introduction to Ellul's book "Propaganda":

  A related point, central in Ellul's thesis, is that modern propaganda
  cannot work without 'education'; he thus reverses the widespread
  notion that education is the best prophylactic against propaganda.
  On the contrary, he says, education, or what usually goes by that word
  in the modern world, is the absolute prerequisite for propaganda.
  In fact, education is largely identical with what Ellul call
  'pre-propaganda' ...

  [Ellul designates] intellectuals as virtually the most vulnerable
  of all to modern propaganda, for three reasons: (1) they absorb
  the largest amount of secondhand, unverifiable information;
  (2) they feel a compelling need to have an opinion on every important
  question of our time, and thus easily succumb to opinions offered
  to them by propaganda on all such indigestible pieces of information;
  (3) they consider themselves capable of 'judging for themselves'.

Ellul's book on propaganda is well worth reading, as is his classic "The Technological Society".