*sigh* Unfortunately this situation can happen in any discipline, Dressage just seems to cop the most flock publicly. So, you're friend may have bumped into one not so great Dressage trainer.
I bumped into a reiner who beat the bejeebus out of his horses.... ALL reiners must beat their horses.
I also know a showjumper who competed at the Olympics, who makes every horse she rides stand on it's back legs. Therefore, every elite showjumper rides their horse so handy that they are forced to rear...
Just like ALL Dressage riders and trainers are elitist snobs.
And all police are corrupt.
And all people from the Middle-East are dangerous.
And all American's are overweight and loud mouthed.
And all Australian's wear Khaki and talk like Steve Irwin.....
Get my drift?
Don't base your entire opinion on a single person of the hundreds of thousands of others involved in the discipline.
I love Dressage, I train in it, I compete in it, I occasionally instruct it. It is a wonderful discipline but yes, some horses just can't do it do the level that their rider wants. The warmblood snobbery is ludicrous, I saved and worked my backside off to pay for my warmblood as a weanling - just like someone will work their butt off and save like crazy to buy a top quality quarter horse youngster, or friesian youngster, or arab youngster etc.
I started out with ottbs, an appy x, a few tbx's, a lease wb that was the spawn of the devil and a few others before I started to ride some nice horses.
The idea that anyone who owns a warmblood and rides Dressage is a snob revolts me.