Dangerous Uncomfortable Truths

How many truths can you name that are hidden in plain sight, upon revelation would trigger a nauseous reflex on the noob so intense he would hate you forever for it?

I'm not talking about the political a-man-who-knows-too-much variety.

I'm talking about Matrix-level truths, something that is so profound they have a rule for it.

NEO: I can’t go back, can I?

MORPHEUS: No. But if you could, would you really want to?  I feel that I owe you an apology. There is a rule that we do not free a mind once it reaches a certain age. It is dangerous. They have trouble letting go. Their mind turns against them. I’ve seen it happen. I’m sorry. I broke the rule because I had to.

I can name one here (link here somewhere), but dangerous uncomfortable truths (flactrum) are not confined to the realm of interpersonal dealings.

Your personal growth and civilizational evolution depends on the uncovering of more DUTs.