Look. I get what you're saying, but I completely disagree. A stallion is still a horse. I'm not saying that you should throw a stallion into anyone's hands. But they're not just for the "pros" as you put it.
Not every stallion has a zillion hormones buzzing around. Some do, I'll give you that, but not all.
The stallions that I've ridden were NOT trained by professionals, they were NOT trained to be amazing competitors, and they were NOT bred from extremely calm lines. In fact, quite the opposite. And still... I found no difference in them from a mare or a gelding.
A horse is a horse. A dog is a dog.
By saying that a rottweiler or a pit bull needs to be watched after more and is more unpredictable than say a chihuahua or a papillion or a retriever, it's just plain bigotry, and just plain stupid. Just because an animal has a history of doing something doesn't mean it'll fall into the same pattern.
Now, you say that I can't talk this way, but if people believe that we come from Evolution, and we're animals, I have every right:
If you came from a background that was full of cruel slave drivers, and you have the abusive "gene" in you, yet, you were raised by kind, loving parents, would you still be abusive and cruel? No. And you'd call it bigotry if someone held the crimes of your forefathers against you.
I've had pit bulls. And let me tell you something FLAT OUT. Pit bulls always were, and always will be the kindest and most gentle dog in the world. The problem is always the handler. Most people say that Retrievers are the most loyal and gentle dogs ever, I scough. Even in a good home, they tend to be a bit rowdy, and in bad homes, they can sometimes be worse than pits or rotties.
And I've worked with stallions. Don't call me ignorant, don't call me stupid, and don't say I don't know what I'm talking about. No. I don't believe that any little girl should have a testosterone high stallion in their backyard. So PLEASE stop acting like that's what I'm saying. What I'm saying is that many people make the ASSUMPTION (yes... I say ASSUMPTION) that stallions are walking ten miles high on testosterone and hormones. And that's false. Hormones only truly act up when a mare is in heat. And most stallions (unless they're untrained and unsocialized) will do little more than prick up their ears and maybe get a bit sidetracked from what they are doing.
I've seen stallions in bad hands. It can be nasty. But every single one of those stallions (without being gelded) with just a little TLC, and some training, has become a wonderful, kind, and gentle horse for (yes) anyone.