This. My parents knew nothing about horses and riding. Plus, back in the 60s, girls sports for younger girls weren’t really a thing. We did dance classes and swimming lessons at the Y, but that was about it, so they didn’t really have much of a frame of reference. For all my parents knew, all that yelling and screaming was just how riding lessons went.
You know, I might approach the parent who seems upset privately and just say, “Not all riding instructors call their students idiots and make them cry. There are other places.” But of course, that’s a risk to you if the trainer finds out about it.