Simply put, it's a minefield when it comes to ethics. Older forms of ABA were straight-up abusive, and uses punishments to train autistic children out of even harmless stims without consideration to the purpose of them(self-regulation/stimulation) and with the intent of making the child 'appear neurotypical'(an unrealistic goal with heavy cultural bias which angers me both as an autistic woman and as someone who is going into speech pathology).

Newer forms are better, and can certainly be helpful, but you still have a LOT of therapists who practice the older form or who are just plain not great at their job. Not to mention that, truthfully, a lot of the newer forms seem to be labeled ABA more because of it being covered by insurance than any true connection to the theory.

Done well, ABA can be good. But it's really easy to run into therapists who decide that flapping is bad, or that it's OK withhold things like food to train a kid out of a behavior. In short, it is at a minimum controversial in the autistic community, and in my opinion parents should be very cautious when choosing and working with a BCBA.