It's actually quite the opposite. You should never stand directly behind a horse while it's urinating.
Here's why:
* Safety: Horses can kick, and they often do when they are urinating. They might be startled, or just have a tendency to be grumpy while relieving themselves. Standing close behind puts you in the direct line of their hooves.
* Hygiene: Horses have a tendency to spray urine quite a distance, and you don't want to get soaked!
The best course of action is to stand to the side or behind the horse, giving them plenty of space.
Let me know if you have any more questions about horse care!