Going back to the ORIGINAL question...
I have no problem with stallions in the show ring or any other horse event as long as they are well-mannered and have an experienced rider on their back.
My cousin had a stud (that actually is the daddy to my horse) that was THE most well-behaved stud you've ever seen. Most people didn't even know he was one until you told them! I had the pleasure to ride him quite a few times. One of the times, I borrowed him for an indoor rodeo when I was rodeo queening for carrying flags and chasing out stock. It was very tight quarters in this smaller indoor arena and he stood between 2 mares the entire night and not one single peep out of him! He was a perfect gentleman and SO fun to ride! My cousin also did western pleasure, halter, and showing with him when he was younger, and now was using him for roping and gaming events and he was getting quite good! Unfortunately, he died in a freak accident last summer.
Broke my heart when my cousin told me about Ravie! He found him lying next to the broken gate. Not a scratch on him and no sign of struggle. The best he could assume was that he was running around and playing in his paddock a little too much and somehow hit the gate, flipped over it, and broke his neck instantly.