interesting article) that corroborate this: it's not just me talking shit.
On positive reinforcement inspiring manipulative and deceptive behaviours: how is that a bad thing? Most high jobs are based around some sort of manipulation of others - teaching a child how to control others is likely to benefit their future career and allow them to avoid conflict.
Kids should also be sheltered to some extent: would you be comfortable allowing your child to watch a violent rape scene in a film, for example? That would probably traumatise the poor little bastard. Even existential truths can be mentally scarring and lead to depression: "The universe does not care whether you live or die, whether your family care about you, or whether you've just been beaten and left for dead." Sometimes people need to be shielded from the truth until they have the resources to deal with it.