I don't think that all showing is abusive, I just think it's counterproductive. The original purpose of showing was to evaluate horses for breeding - and it's not even the best way of doing that - but now it's just about bragging rights and money.
I want to start with, I respect your opinion, it is yours to have. Although I may not agree with it completely, I do know there are a lot of people who show for the reasons of Money or bragging.
I however LOVE to show my horse. I am not looking for bragging rights, and I don't get any money out of it, in fact... I loose money ha ha.
Why do I show? Well, here is my reason. I bought my horse as a 7 year old pasture pet that had for all intents and purposes, been given up on. He had a history of an abusive "30 day training" and bucking people off after that. Then I bought him and reworked him from the ground up. I decided to go with dressage to teach him to move more properly, use his body, an be balanced. I show him dressage because I like to see that we both are improving. Most people say our scores SUCK. But I think my horse is great because each show we get a higher score...
As for abuse. I saw it at some shows when I lived in California. I have NEVER seen it here in Nebraska. In fact, they are pretty strict about that out here. Not just show officials but the people at the shows. Yes you often have to know the whole story, but people are not afraid to ask "what is going on that you need to do that to your horse?" I've seen trainers help people who aren't their students at a show because they see an issue escalating to where the rider is just freaking out. I have been mostly to dressage shows, but I have also been to some of the APHA shows, and AQHA shows... I think the most abusive thing I have seen out here is an occasional "bump" with the reins...and most of those people get yelled at by their trainers for it too.
I think if everyone all over decided to SPEAK UP at shows, ask questions, let show authorities know what is going on, then there would be a lot less abuse at shows. It works here in Nebraska, so why not other places. I think a person who sees someone doing something abusive but doesn't speak up or at least question what is going on, is just as bad as the abuser themself.