I have to add my two cents worth here. From personal experience. I owned a 5 year old miniature stallion, he was incredibly well behaved at home, and yes I had used him to bred mares. Personally I don't care what sex a horse is, I demand manners from all. Now a little more about my 5 year old stallion:
We took him to his first show and holy moly he was a real jerk. Halter Class or performance in hand (he wasn't broke to drive) he was "on the muscle" all the time. We jokingly asked the judge if you could get "peter" faults in Hunter and Jumper classes, that is how he was most likely to knock a rail off. Unfortunately our next show was only two weeks away and already entered (although the thought crossed my mind to leave him at home). I will say we did not let him get away with an inch, he was disciplined for every little wrong move and any loss of focus at the first show.
Took him to that second show and he was a completely different horse. Calm, never on the muscle, never trolling for a woman. I really think it was just he was over stimulated on his first trip away from home. Several of the judges at the first show were at the second and couldn't believe the difference. Honestly I can tell you that we did NOTHING differently, he traveled in the same trailer with the same horses (all geldings) and was handled in the same way. We were prepared to scratch him from all classes and just handle him on the show grounds as a life lesson in manners.
i have since gelded him because he was being sold to a family relatively new to horses. They didn't care if he was a stallion, I did. The purchaser paid for the gelding and I took care of getting it done and the aftercare etc that way I knew it was done and he was all healed up without any complications. He was delivered to them a happy gelding six weeks later. (He sure has packed on the weight since then!)
if I would of kept him he would still be a stallion. He was really one of the easiest horses to handle, except for that first show.
For your stallion - Was it his first show? Has he done this before? Does he do this at home? if the answers are No, yes and yes, then geld him and make him happy.
I am not sure how old you are, your profile doesn't say, but I know there is an age minimum for handling stallions. I think it is 16, if you are less than that I would definitely geld him.