Ayahuasca retreats are a scam to relieve drug tourists of their money. I prefer my psychedelic experiences not to start with an hour of projectile vomiting into a bucket, but some people think they have to "earn" a trip by putting themselves through an ordeal. The reality is that botanicals can be dirty drugs with a high body load just like synthetics can be. Also MAOIs can be unpredictable in the magnitude of their effect, and can prolong trips much longer than you bargained for, based on small details of your body chemistry and recent diet.

As for the "latent" comment: using psychedelics can be a stress test, and (as they say of investments) past performance does not guarantee future results. I've had entirely positive experiences with psychedelics, but also know that they're powerful substances that should be used sparingly. People who advocate "heroic doses" are doing so with no concern over the casualty rate. It will go bad for some people, you can't always predict who, but the odds worsen with dosage and frequency of use. So to me, the "latent" pseudo-explanation is a bit too much like "and if it breaks, it needed replacing anyway." Too self-fulfilling to be credible.