[bsanr2]

I don't I know the answer is that difficult.

1) Prime Directive: don't introduce knowledge that will make someone's life harder or more complicated if you don't have to.

2) If they have the means to get that knowledge, you're now obligated to fill in the disparity between your quality of life, such that they can be at least as happy as you are.

[wrkronmiller]

This way of thinking is founded upon the notion that blissful ignorance is something societies should strive towards.

Without unfulfilled desires, there is no room for self-actualization. See: Maslow’s Hierarchy of Needs

[bsanr2]

This is less about what one should want for oneself than what one owes others whose lives they are disrupting with their presence. If you take someone's innocence, you have a moral obligation to their mental well-being.