Are you ever forced to work with people who are untrained and who do far more harm than good?

I used to substitute teach in the 90s. I recently got back into it almost full time. Something they have now that they didn’t have then are teacher’s aids out the wazoo.
Some of them are patient and helpful, but some of them are obnoxious and rude, verbally abusive to the kids (in my opinion.) We spend an entire semester in college on classroom behavior control, how to encourage the good and discourage the bad. We are taught to model the behavior we want the children to display. We are taught the importance of body language to convey authority and confidence. We are taught how important merely walking past a child can be, even if you don’t say anything to them. Or if a kid is talking while you’re telling the class something, stopping talking in mid sentence gets every one’s attention, everyone looks at you, including the kid who was talking. When he looks up you’ve pinned him with your eyes and just imperceptibly shake your head.
Never in there did they suggest that screaming at a kid, insulting them and belittling them is acceptable or effective BECAUSE IT ISN’T.
There is this one 4th grade class room that I’ve been in several times. The aid is a huge, obese cow and she screams at the kids and literally throws her weight around to scare the shit out of them. Monday she planted her fat ass in front of a kid, slammed her hands down on the desk, got in his face and screamed “YOU ARE IN FOURTH GRADE! STARTING ACTING LIKE A 4TH GRADER INSTEAD OF A BRATTY 2 YEAR OLD!!” Man I wanted to throw her out the door so bad. Thank God she was only in there for an hour, but for that hour, by God, she was gonna show me how it’s done.
I guess she figures if I’m not screaming I’m not in control (which is not true) so she’s going to scream for me. I guess she figures that if I’m using a normal, conversational voice to address a trouble maker I’m ineffective. Also not true.

I was in PE today. I had the class under control to my satisfaction. They were doing fine. But the aid just kept nagging and nagging at them over every little move they made. “Marcus! You need to look at the teacher when she’s talking to you! Marcus! Look at me when I’m talking to you! Marcus!” Nag nag nag. I kept having to stop talking because she kept talking. I just wanted to scream SHUT UP!!
I don’t know what the hell I can do about this, though. The regular teacher and the principal have to know.

Have you found yourself forced to work with incompetents but there was nothing you could do about it?