At a barn I worked at we had a few horses that did this, however we had automatic waterers so once the horse pooped in it they couldnt drink! They were placed near the corner, so for most of the horses it was solved by nailing a board angled across the corner in front of the waterer. The horse could lean over easily to drink, but it was harder to back up against it to poop. There was still one horse though that pooped in hers every day, so we all would check her stall a couple times a day with a giant slated soup ladel to fish the poop out.

Before you criticize someone walk a mile in their shoes. That way you'll be a mile from them, and you'll have their shoes.