Whilst I fully respect that the OP created this thread for discourse on aggression in retriever breeds, she cannot continue to make sweeping generalisations about clueless owners not training their dogs and expect the thread not to deviate.
Not all dogs can be safely walked off the lead and this is not always entirely down to novice owners who can't be bothered to train their pets. I make no apology for pointing this out.
I have a dog breed from an ancient and primitive group of dogs - the Livestock Protection Dogs. They are, from necessity, independent minded, bred to largely work off their own initiative and their recall is notoriously shaky at best.
Of my 9 LGD over the last 47 years, I have only had one that had 100% reliable recall. That really had little to do with training and was almost entirely down to her individual temperament. She was from working bloodlines, both her parents were French imports and she had no interest in people. She was aloof to the point of rudeness, closely bonded to both of us (self and partner) and she never strayed more than a few metres from us on a walk.
None of my others has had a totally reliable recall. All but two of the 8 Pyreneans were from European bloodlines with some working strains. Three of my four males could be allowed off the lead in certain places, if it was quiet with no people around, but two of the four bitches could never, ever be trusted off the lead. It was not from lack of training but entirely temperament based.
There will be exceptions, I have no doubt that there are people with very well-trained LGD, but by and large it is rarely safe to allow this type of dog off the lead in a public place in most areas of the UK. This is not for reasons of aggression but down to the way their brains work; if they see a speck in the far off distance they are duty bound to go and investigate in case it could pose a threat to the flock, which, obviously, with a pet LGD, is its human family. Their perceived need to protect you will almost always override their willingness to respond to your commands and you have to remember that they mostly work alone when guarding. They will roam for miles and it is just not safe in the urban UK. So yes, you can train them - to a point - but there is always an element of risk in allowing a LGD off the lead; the fear of them getting onto roads and the awareness that dogs of this size and strength, no matter how calm their temperament, will be seen as a threat by many people and most smaller dogs. This is what makes them unsuitable as urban/suburban pets for the "average" family, they need dedicated owners with some understanding of LGD working traits and heritage.
So I have to disagree with @Killingoffmyflowersonebyone because it isn't always about poor training or an off leash dog "living the life it deserves". Not everything is that cut and dried. Sometimes the life they deserve is to be protected from danger. There are many reasons for a dog not being well-trained in the conventional sense and it isn't always about clueless owners.
I agree with @stayathomer that not all dogs need to be off the lead in public. We have a secure double fence around our garden and we also lead walk for miles on footpaths and bridleways. Our dogs are perfectly happy.
I will tell @EdithStourton and @schloss that I feel there is a difference between training and teaching. I have never crated my pups, I gently teach them from 8/9/10 weeks what is "acceptable" behaviour in the home and they learn adult behaviour very early. I never have resource guarding, I used to feed three adult PMD together in my kitchen. We work on mutual respect and trust - because, with a dog that weighs more than you do, there is no point in trying to push them around. They are well-socialised with people and dogs, anybody that comes into our home will be welcomed. They love children, are 100% trustworthy with my cats and around livestock (always, of course, on the lead around livestock) because they have a very low prey drive. At home they are calm and quiet. We like to try to understand how their minds work, we can't expect them to learn in the same way that a hound, terrier or gundog will because they aren't able to. But they are highly intelligent and very fascinating to spend time with. We have never bred a litter and have only occasionally shown, but we have 100% commitment to the physical and psychological well-being of our dogs.
So, I happily admit that I may be a clueless owner in that I don't have well-trained dogs in the conventional sense, with a reliable down, stay and recall etc. However, I can honestly say we have never had any issues with aggression, problem barking or destructive boredom. We like our dogs to be free-spirited and independent minded because the breed standard calls for "quietly confident". We absolutely do not treat them like babies; that is something I loathe about modern dog ownership. But we do allow them to retain the inherited traits of their breed/group without trying to train it out of them. And before someone leaps on me, no it is not "dangerous" to do that. The dam, older sister and now brother of our 7 month old puppy are actually working dogs on farms. Allowing a LGD to be a LGD is no different from allowing a gundog to work as a gundog. All you do is channel their inherited behaviour in the right way.
I apologise for the off-topic essay but I think it important to put forward the point of view of those of us who do not let our dogs off the lead for reasons other than the fact that we simply "cannot be bothered" to train them. I am sure people will disagree - the OP for one. But a LGD should not have the behavioural characteristics of a gundog and I fully stand by my observations here.