https://www.bartleby.com/278/2.html
It's completely true that four year old boys get erections and play with themselves (I did), don't think about it all when they are ten, and then tend to think about it a lot when they hit puberty.
It is the basis for understanding how sexual abuse hurts children, but say it and people will report you to the FBI as a pedo.
If Graham were serious he could make a list of 20 diverse examples like this.
"When you find something you can't say, what do you do with it? My advice is, don't say it. Or at least, pick your battles...The most important thing is to be able to think what you want, not to say what you want. And if you feel you have to say everything you think, it may inhibit you from thinking improper thoughts. I think it's better to follow the opposite policy. Draw a sharp line between your thoughts and your speech. Inside your head, anything is allowed. Within my head I make a point of encouraging the most outrageous thoughts I can imagine. But, as in a secret society, nothing that happens within the building should be told to outsiders."
If anything, it's criticism of Freud and his theories, outside of strictly science-based objections, that is "unsayable":
kevinmacdonald.net/chap4.pdf
pg might be interesting again if he said what "unsayable" and "aggressively independent-minded" things he actually wants to say, and I wish he bloody would - we've got no choice but to read it.
"independent-minded" is such a cliche now - it's often a euphemism for something else. Surely more truly "aggressively independent-minded" people are homeless addicts, not rockstar founders. What's the right balance between conformism and independent-mindedness? In what areas of life? This 2-axis system is way too simple. Start there, dude.
By implication pg (and YC) recognise and value independent-mindedness - but as you say, from the outside YC appears to reward conformism to their well-understood creeds (as well as just playing the odds of an enormous number of companies, rather than being clever pickers).
(edit: removed snark, however deserved)