Well I personally think its rude to discredit any discipline on the basis of prejudice. Everyone is entitled to their opinion, but I would receive a lot of backlash if I went around saying "oh I hate this breed their so ugly or they serve no purpose.. etc." My opinion is that if you don't have anything nice to say, don't say anything at all.
I've ridden many seats. I started at a hc hunter/jumper farm, I've taken my Morgan gelding Hunters, Jumpers, Western Pleasure & Eq, Hunter Pleasure & Eq, and Dressage. I've driven horses, and I ride saddleseat. I've also taken polo cross & sidesaddle lessons. I would ride a thoroughbred around the one mile if given the chance, same thing with a standardbred (well er drive). I currently ride at two H/J farms and ride a variety of breeds, in addition to the farm where I keep my horse. But my favorite discipline is saddleseat. I'm in the finalization process of a new morgan filly (yay me!) who I want to take saddleseat hopefully English Pleasure.. but she's a long way from the show ring since I'm training her.
My point is a horse that does its job well is a beautiful thing, no matter what breed it is or what its job is. Everyone will have their likes and dislikes, but its not fair for you to be judgemental (at least publically, your private opinion is yours and no one can take that from you), especially if you've never tried saddleseat. I would never say anything negative about a discipline or breed I have never tried first. I certainly wouldn't start a thread intended to bash a singular breed, horse, person, or discipline.
Now to addess your concerns, 99% of people in the industry (especially Morgans, I can't say for other breeds since I've never been to other breed shows) are not abusive. Just like (I hope) the people who stick tacks in rails of jumps and bump the horse's knees as they go over are in a one percent of their own. Or just like the people who leave the horse's standing knee deep in mud with no food or water, on the brink of death, are in a 1% for the industry on a whole.
Things you might of seen or heard or assumed.
"The horses are forced to pick their feet up in a way that is unnatural." Not true, it is something bred into them. True it has evolutionized to the extremes you see today, but not without careful selection. I've put action chains (like bracelets, encourage the horse to use legs in a more upward motion) on my gelding (who has some of the breeding, but became a WP WC instead) and he does nothing. He's also not the type to snort or flag his tail, and he's not "hot" or excitable.
"They tie the feet together and make them move." Technically, yes. However there are reasons and its not nearly as harsh as it sounds. The tubing is breakable, so a horse using it ineffectively or it will break, it also doesn't inhibit the movement of a horse who's inclination is not "flashy." (like my horse) It's the same material as the resistance training tubing in gyms.. You can buy it at modell's for yourself (w/ two handles at each end). Just like you wouldn't jump a horse in the grand prix without thorough preparation, you wouldn't take an unexercised horse in the show ring. If you did, injury/founder/overheating could result. The stretchies build muscle, it's like resistance training. The horses won't use them if they don't know how (like my gelding, he won't).. "knowing" how is genetic, there's no other explanation.
"They grow the hoof to an unnatural length and add weighted shoes." Really the length of the hoof provides support during show season. The weight of the shoe and pad give the horse something to "pull" against (similar to the chains or stretchy tubing provides). Most times the shoes are taken down in the off season. Also the divisions place restriction on toe length and weight. For example Classic Pleasure (the least of the three for Morgans) has requirements that the association sets for all other disciplines (hunter pleasure, western pleasure.. and I think the sport disciplines too.).. Which is basically nothing..
"They never turn their horses out." I'm sure many farms don't. But during the show season, the horse's can't be pulling shoes constantly so they are turned out minimally or handgrazed. If they don't have shoes on there is generally no reason for them NOT to be turned out. Again it varies by farm, and some horses never see the light of day, except for the walk to the arena or round pen, which is sad.. but I definitely don't think its the norm. Babies, broodmares, and lesson horses are almost always turned out appropriately.
"The horses are scared to death, that's why they do it." Horse can be silly, but if the horse was truly scared to death it would do the normal scaredy cat horse stuff. It would bolt, rear, sidestep, bulge its eyes, etc. The common tactics used by trainers are to excite a horse.. get them in that mood to do their thing. Baby Powder might be a little scary for a first time horse, but it smells funky and puts a lot of horses in that mood. Plastic bags make noise, noise gets the horses excited. (hence why all the trainers line up on the side of the ring and whoop and holler at classes.) People have other weird customs but those are the two I generally use. Some people bang the fence board to make some noise. A truly scared horse would rear/run away.. not pick his feet up even higher?..
"The horses are miserable.. pin their ears, bite, crib, develop other bad habits." None of the horses I'm around do any of these things, they generally trot happily with their ears perked- as if they wouldn't be anywhere else in the world but in the moment. They know they're fancy and they know people love the way they move. Horses who have pinned ears at Morgan shows wouldn't win.
"They ruin the horse's tail in order to have that "flagging" tail look." That's mostly done with saddlebreds, I'm not sure if it is still done or not.. But I would never do that to a horse. In Morgans its illegal to do anything of the sort, including adding tail extensions. So yes it does happen, but many people do not condone it or partake in it.
I'm sure there are plenty other rumors, so feel free to ask for clarification on any of them and I'll tell you my honest opinion.
As someone who has ridden many seat types, nothing beats the exhileration of riding a horse who truly loves to show off. There's no explanation, but I would reccomend the sport for anyone, plenty of wonderful horses who are excitable but not moronic (some morons too, believe me) and its fun! The only downer is it CAN be expensive, but you can find great deals on tack and clothes on ebay..