I happen to agree that negative psychedelic experiences are just as much about nurture as nature. Your preconceived notions about what will happen, anxiety of the unknown and any emotional baggage you just might be carrying around that day all play a huge part in determining what kind of experience you will have.
I consider myself an experienced psychonaut and as such I approach every experience with respect and humility. When considering some of the more ineffable ethnogenic compounds such as DMT in which total ego erasure can occur in less than a minute, I consider the Psychadelic a sacrament and act accordingly. Possessing an attitude of humility is the only sensible approach when dealing with a compound so far beyond my understanding that no frame of reference is available and you are entering another realm in which you yourself are the alien. Not the self transforming elf machines that seem intent on clowning their way through this inter-consciousness meeting of minds.
I am now a science fiction author and almost all of my work deals in some way with the notion that the world is not what it appears. I. I have a debt of thanks to psychedelics and Ketamine in particular for definitively proving to me that absolutely anything is possible.