I don't agree that late gelding causes bad behavior. Some horses are have more dominant personalities then others, and you have to be extra vigilant in being their leader. Once they are gelded their testosterone levels drop, they don't have lingering affects of their testosterone. If they have been allowed to be aggressive, pushy and disrespectful as youngsters then they will still be pushy and disrespectful once gelded. It is all in the training and you cannot make excuses for bad behavior you need to be a leader and fix it.
My gelding was gelded as a 4 year old, when I got him he acted like a breeding stallion and his hormone levels were through the roof. The vet cut him open removed testicular tissue on the left side. Four months later his testosterone was still high, and he was still acting studdy, aggressive, pushy and I could not turn my back on him. I chose not to do another surgery and decided the best course of action would be put on my big girl pants and be a leader. I instilled a zero tolerance for disrespect policy, and work him six days a week. He is now a gentleman, I can ride him with mares no problem, and I am competing on him with hundreds of other horses around and no one would know he what he is. The only thing I cannot do is turn him out with mares, all heck breaks loose, he has climbed a fence to get in with the mares once, but we fixed the situation hot wire is great stuff. But when he is with me he is great but I don't put up with any disrespect and all it takes is a look from me and he says yes mam.
Be the leader your horse needs you to be.