I think a big mistake parents make is the assumption that your kid is actually going to listen to you.
There comes an age where they realize they'll do what they want to do. By punishing your kid for the descisions he/she makes at that age, they'll just not trust you with anything in the future.
IMO, the best approach is to educate them as best as you can, warn them of the truth, actually acknoledge the lies told in schools and on tv, and try to send them off with the protection of truth. Not the pain of blind consequence. It's sad how stubborn my parents were. Eventually, you create whole alternative lives for them to admire and leave you alone.
All becuase of the stubborn blind inability to actually question your own ideals and perspective.
Then there comes the day that the parent stops trying to fashion their child in their image, and see them for the person that they truly are, a completely unique human with it's own feelings and dreams and desires.