I hate it when a horse stops to poop while I'm riding. I was training a horse, that WOULD NOT move while pooping. He never slammed on the brakes, but he'd wait until we were walking, and he'd stop. I squeezed him, I kicked him, I tapped and smacked him with a crop, I used spurs with him, and it didn't matter what I did, he wouldn't move until he was done. No idea where he got the idea he had to stop, as he did do jumping shows, and I'm sure that the rider didn't let him stop, and the current owner, the previous owners mom, didn't ride much, and hated him stopping, so no clue where it came from, but every time he stopped I made a big deal out of it, and tried to get him going, and never was able to get him to GO even at a walk while pooping. I'd have been happy with even a step or two forward just to begin with. That being said, to each his own, and if you want to let your horse stop and poop, that's your perogative, just know that it's not allowed in shows, you will get docked points or disqualified if the horse stops, and if you are planning on selling the horse, or leasing the horse out to someone who may one day show, it does inconvenience them if the horse has learned its okay to stop to go poop.