This is a really nice read if you have some time.
Propaganda works by appealing to our most base, animalistic instincts. It does not appeal to our better nature, although one of the purposes of it is to convince us it does. It pretends to appeal to our reason, when in fact it appeals to our most primitive emotions. There is good reason for this: perception travels through the emotional brain first, to the rational brain last.

Also, check out this documentary called Century of the Self, its long but very interesting; make sure you watch all 4 parts.