I had 2 Jersey gomer bulls. 1 was no problem at all. Of the 2 he was the least active on the cows. The other bull was a little different story. He associated me as a threat or competition. A crack across the nose when he was about 1 1/2 years old kept him away for there after. If anyone has ever read some of my previous posts about not inflecting pain as it may only lead to more aggressiveness, this may seem hypocritical. When a bull is in the attack mode (protecting his claim to his herd of cows) I will do what ever is necessary at the time. This is not much different than 2 bulls deciding dominance over the herd. There is a lot of difference between working cattle in a lot and the way they act in the pasture. When in the pasture I always carried an electric fiberglass post when there was a bull around, of any breed.
I have read several posts on here about people being hurt or killed by mean bulls. I believe you may find, if there were statistics, that many more people have been hurt or killed by the gentle cows and bulls they thought they could trust.