It's no different from any other potential for abuse from someone with power - the way to mitigate it isn't merely to try pick good people (of course, start there), it's to wrap the vulnerable elements in protective practices and institutional controls to prevent abuse if an individual actor fails to live up to the standard.
For example, in the biggest abuse scandal of our generation (sexual abuse by Catholic priests), it's not just that the priests did great individual evil but also that the institution itself utterly failed to do anything about it or even abetted it.
However, the illicit nature of psychedelics makes those kinds of controls or institutions impossible or very hard to put in place.
Finally, for the abuse in the MAPS MDMA trial (which was 1 patient out of 200 participants) to be used as evidence that psychedelic therapy is more prone to abuse, you'd have to look at the rate of abuse among therapists and psychologists as a whole to know if it's par for the course or something extraordinary.
Bad actors will try to take advantage of the vulnerable -- and these drugs put you in a more vulnerable position than otherwise -- so your warning still stands. I just don't think these issues are unique to this stuff other than the legal status.
