Naive, youthful optimism is healthy for their cognitive and psychological development, though. If they get black pilled very early, especially in their formative years, the sheer force of nihilism coupled with the realization of biological determinism will be an impediment to their personal growth and any positive motivation to do good things for themselves (schooling and education, healthy diet and activities etc.).
Think of the black pill like a very potent drug. It needs to be taken once the mind is mostly crystallized. Taken early will damage it, possibly beyond repair. The black pill is pure, raw, undistilled truth. It can be devastating to a mind that isn't on an adequate foundation. Of course, individuals differ, but as a general guideline it's prudent to black pill people in their early adulthood, than it is to do so in their early-mid teenage years.
Please note that this is not advocating the blue pill. Yes, there's a high risk of being blue pilled in adult life due to societal indoctrination in the formative years, but I truly think that early exposure to the black pill may be catastrophic. Take Elliot Rodgers, for example. That nigga was black pilled early, so much so that he wrote a full manifesto. The black pill made him aware of a lot of nasty truths, but he lost his mind as a result and went... ER.