There are few things that frustrate me as much as irresponsible pet owners who don't respect other people that their animal impacts. I also think they're the majority. Dogs belong on leashes - period - unless it's an off leash dog park. END OF STORY. My dog is as friendly as it gets - he's a social as it gets - but he's still an animal, he can still be unpredictable and he still belongs on a leash. EVERY TIME. And my dog is better behaved and more under control than most. I'm a dog lover - and I can say that you did nothing wrong, the owner did. It's unfortunate that the arse hole owner caused that to happen to you and his dog.
I have mixed feelings about mandatory insurance only because it might discourage dog ownership and there are so many unloved animals as is. In terms of principle - they should require insurance. I am firmly in favor of greater liability standards in holding pet owners accountable for the pets, both civil and criminal. If your unleashed dog bites someone, I am in favor of an assault charge.