I've been following this thread with interest...
Saffysmum - you do have a point, and it's the first part of your post that is a major point - dogs do not have the freedom to roam that they used to have... they spend far longer confined and rely on owners to create opportunities for socialisation and exercise... a lot of owners don't do enough to meet this need, and a bored, under-stimulated (or possibly a better phrase is inappropriately stimulated) dog can easily become an aggressive dog. The more aggressive dogs there are out there, the greater the chance that an appropriately cared for dog can develop behaviour problems because of being attacked... so the problems spread...
In the past dog fights weren't problems of aggressive dogs, they were "handbag" fights to sort out differences of opinion and social standing... very different to any dog with aggression issues.
As the owner of a dog who could easily have been described as "nasty" by owners of other dogs she grumped at in the past, and the daughter of someone who has a seriously dog-reactive Border Collie (caused by aversive training methods), it is VERY trying to walk a dog with issues... it has taken a lot of work to help Honey with her confidence issues, and to learn when she is justified in telling another dog to get lost (and when she isn't!). It can be very demoralising, and you can get to the point where you dread meeting another dog on a walk... fortunately with some great advice from here and a lot of work from us, we have got Honey to a point where, while she might be grumpy, she can generally deal with situations - I am more confident that when she grumps she has a good reason to do so, and I know she isn't going to escalate into full-on aggression. But there is still an element of stress to walks - if I see a dog I know she's likely to lose patience with I admit I get a sense of dread (because of the other owner normally failing to acknowledge that their dog is rude...
), and I don't trust other people walking her, as they won't read her body language and get her out of situations she can't handle. I have learned a few stock responses to owners who react as though Honey has eaten their precious little dog (non-confrontational responses, along the lines of "Oh, she really doesn't like her bum being sniffed" or "She can be wary of really bouncy dogs" so that I am acknowledging her behaviour but explaining it rather than blaming anyone...) and I find that helps keep my stress levels down.