Lying "for good," whether to kids or the public, only works as long as you hide the fact you lied. The minute the public, or kids, find out it was a lie, they begin to question everything else.
It's actually hard for me to make up my mind about global warming. Why? Because there has been so much lying, deception, and contradiction involved in the entire debate. Rather than making me think even more seriously about it, it makes me want to just totally ignore it altogether because it apparently isn't important enough to tell the truth about.
Want to convince me of something? Tell me the truth in such a way that you can back up your claims. Want to turn me off? Lie to me and then say that you were just trying to convince me because you knew I wouldn't believe it if you told me the truth.
(bonus points: make it a political argument. ;) )