Ask a parent! Kids can be very wary of attempts to "shape" them. Of course they're not going to know the word propaganda, but the instinct to detect manipulation (and react negatively to it) goes deep.
Indeed. Also, small kids are excellent bullshit detectors. They can tell when they're being given non-sequiturs, or explanations are inconsistent, and they (rightfully) see this as problem and are confused when such things come from sources they trust (e.g. parents).