I think you explained it perfectly. I think we can carry the analogy a bit further. Even with my best interest at heart, my parents will do what they think is best for me and will nudge and push me towards what they think I need to do.
So even assuming that the powers that be have our best interests in mind, they are still people and are prone to make false assumptions about what's best for us.
And to further your point, I want to see the good in people and believe that those who hold power in positions in the State want to do good, and will do what they think is best, but that doesn't necessarily mean it is. The problem is when the State fails, whether it is because of incompetence, misunderstanding, misguided intentions, or true intent to do harm, those who are dependent upon the state are the ones who suffer.
So even assuming that the powers that be have our best interests in mind, they are still people and are prone to make false assumptions about what's best for us.
Are you talking about this essay? http://www.paulgraham.com/say.html