What's wrong with ABA therapy? Genuinely asking.
It was literally created by a guy that did not believe autistic people were human - his words, not mine. It's not real therapy, it's just abusing autistic people (mainly children) until they associate doing any autistic thing (stimming, not looking people in the eye, giving only non-verbal answers, not being comfortable with hugs, etc) with stress and pain, so they "fix their behavior".
The entire thing is based on the completely bullshit assumptions that any trait of autism is inherently negative and has no real functionality, both to the person with the condition and to those around them, and that they can just learn how to do things "the right way" - hence the name Aplied BEHAVIOR analysis. It assumes we just "don't know how to act", like a little kid that hasn't learned to spell or how to eat using a knife and fork.
But the thing is autistic people behave the way they do for a reason. "Ordinary" things (like looking people in the eye, or always hugging their relatives and friends, or having to be in a crowded room, with a lot of people talking at once) are PAINFUL to us. Some of us can mask how much it bothers us, but it never stops being a problem. And on the case of stimming (saying the same word over and over, running around, flapping ours hands, biting on a toy, etc) that is what we do to self-sooth when something isn't going right.
ABA is abusive because it forces the patients to behave in a way that causes nothing but pain, just because that's how neurotypicals behave naturally. It's like punching someone in the face over and over, telling them that if they complain they'll just get punched again, and then using the fact that they're not complaining about being punched anymore as "proof" that you made them no longer feel pain - when it's pretty clear they're only not complaining because they'd be punished with more pain if they tried.
Not to mention: training a bunch of vulnerable kids, some of which cannot talk and don't even understand what's going on, that if an adult does something that bothers or hurts them, including touching their body without permission, it's their job to just sit there and take it and that if they turn to their parents for help they'll just get scolded for it because, again, the whole point of ABA is to go "This is all your fault actually, stop crying" is a HORRIBLE idea. It's practically grooming kids to accept that any and all forms of abuse (including sexual) are things that are supposed to happen to them.
That's why one of THE most repeated phrases by autistic people who speak out against ABA and organizations like Autism Speaks, an AWFUL hate-group pretending to be a charity and that adores things like ABA or trying to to blame everything from vaccines to milk for the "rise in autism cases" (which isn't actually real), is "Nothing about us without us."
The overwhelming majority of treatments and charities that claim to help autistic people are only doing things that are either useless or downright harmful to us because they all start from the basic misconception that we don't understand our own condition, that we cannot possibly know what would help us, and that we need someone else to "decode the mystery" that is autism to "save" us.
Entire decades of wasted effort and money, as well as abuse being pushed as a solution, could have been prevented if non-autistic people would fucking LISTEN instead of speaking over us just because we act "weird." It's all based on "Your condition bothers ME, therefore I'm the one who decides what is or is not a problem for YOU." It's the most condescending bullshit ever.