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For the first several years, a parent has to substitute their judgment for their kids judgment. This can be done honestly and firmly. Try to minimize exposure to dangerous situations. Tell them "this is dangerous for you, stay away."
At some point, the kid has to start making their own judgment. The parent has to give the kid the best tools for making those judgments and then just trust them to make the best decisions they can. This can also be done honestly.
No parent can expect their kid to make all the best choices. Goes without saying, but I'm saying it anyway. The LW has pretty good judgment tools. The kids she refers to do not.
When you are dishonest in training your kids judgment I believe it will catch up with you. The more lies you tell, the more the foundation of the kid's judgment will be weakened as the lies unravel.
Lies like: marijuana makes you psycho. Don't learn about sex, it'll just make you want to do it. I never did drugs.
When the kid discovers that for instance marijuana doesn't make them psycho, they wonder what else is untrue. Maybe LSD is a good idea too. And maybe coke.
(Note: my oldest daughter just turned 13. I may have different opinions on this in 5 years!)