I own an aggressive dog. When we go on walks, he is on a lead 100% of the time.
Just remember that having your dogs on a leash is as much to protect them from other dogs as it is to protect other dogs from them.
If your dogs had run up to mine like that, they could have very well been bitten by a frightened animal. Would it be my dog's fault? He's on a leash. He's right next to me. You breaking the leash laws would have resulted in the injury. I don't know if I would have kicked out at your dogs, but I would definitely be trying to keep them away from mine for their own good. And the fact that I had to protect my dog from yours at all means that you do not have enough control over your dogs to let them off-lead.
So, while the swearing may be out of line, if he has an aggressive dog, he's trying to protect your dogs as well as his as you're standing there smiling as if it's no big deal. It's a huge deal.