Honestly, ABA used to reduce violent or aggressive behavior is still bad. It's less overtly abusive than what the above poster described, but it still uses the same methods.

If a kid is frequently screaming, ABA practitioners will completely ignore the child to "teach them not to yell," and will tell parents to do the same. Eventually, the kid will stop yelling — but not because he understands that yelling is bad.

Never does the practitioner or the child's parents question why the child is yelling. They do not attempt to meet the child's needs that they are trying to have met. They do not try to understand the child's behavior. They just train him to stop yelling, without making any effort to improve the child's mental state or help cope with what distressed him in the first place. This doesn't teach the child to communicate in a different way — it teaches them that they can't rely on adults to meet their needs at all.