We aren't very rational, when it comes down to it, because rational people have trouble making decisions. Political issues are hard to visualize or experiment with - they seem to be distant from daily life - so most people, in a "natural" state, will lack strong opinions on any given issue.
Thus, "coaching" comes into play - people rely on things they've been told to guide them, whether or not it was correct information. Most of these political tactics act as a way to both inform people and influence them. This can be "good" when the tactic is something that adds a healthy structure and process to governance - for example, the concepts of civil liberties had to be both invented and then propagandized in order for people to comprehend their value and demand their existence. People living in tyranny weren't necessarily _happy_, but they didn't know of a better option, and couldn't hope to convince others around them.
Of course, it's a "bad" practice in that when speaking of single issues, the same influencing tactics tend to form an unbalanced opinion, by removing some concerns and inflating others into bogeymen. But it's by far the cheapest way to build support for an issue, so it remains the way things are done.
In any case, concrete action is usually the very last step, and almost an afterthought, in the long cycle of debate typical to political processes.