On my daily walks the dogs I most often have issues with are collies and labs.
I'm fairly sure it's because chav d******d f***wits don't have the emotional or empathic intelligence to understand that these dogs need mental stimulation.
Yes.
But the problem goes much deeper, as I said before, dogs have been bred for centuries to do a specific job of work, not to look pretty. When people are stupid enough to buy a dog without knowing what it was bred to do, problems are almost bound to result.
My own history . . . From about 1970 I trained dogs for obedience competition, and competed at Championship level. My first competition dog was a crossbred spaniel, all of the others were German Shepherds and Border Collies, all extremely well-trained and kept very busy, all were perfect. When I stopped competing (young family, very long driving distances and shortage of time and money) I became a problem dog trainer. I was very successful and sorted out nearly all problem behaviour in one visit, basically training the owners but pretending to train the dogs
Guarding Breeds: Rottweilers, Doberman Pinchers, German and Belgian Shepherds, and many less popular ones. These dogs can be great, but they are intelligent, have a strong guarding instinct and need to have work to do.
Gundogs: Labradors (but black labs are generally OK, yellow labs less so and red labs very much less so:. Golden Retrievers, Flatcoat retrievers, poodles, Pointers, all generally OK because their instincts are there but not very strong. Weimerana bitches generally fine, entire dogs are often aggressive. Most spaniels are fine, Springers and Working Cockers are great but are always looking for work and desperately need to be busy all the time, which is why they are excellent as drug and search dogs.
Border Collies: As mentioned earlier, very intelligent and with a very strong working instinct. Bred for herding cattle and sheep, not as pets.
Corgies: Bred for herding cattle, nipping at their heels, so no surprise if they bite people too.
Hounds: Beagles, Bassets and similar, they just get their nose down and follow scents, most can't form a close relationship with humans.
Huskies: Bred to Pull, most can't form a close relationship with humans.
Fighting dogs: Pitbulls, XL Bully Dogs, Akitas. Often OK with people, unless they get over-excited, at which point their fighting instincts can take over.
Terriers of all kinds: Bred for killing rats, very likely to bite anything that moves quickly.
Inbreeding has always been a major problem, especially where there is a lot of money involved. It's the breeders who cause or exacerbate most of the problems. We have laws about incestual relationships/inbreeding with humans, but not with other animals, and this is wrong. If you want to know how badly inbreeding can affect people, look at the Habsburg dynasty - an extreme case, but all European royal families seem to have some degree of inbreeding. And, relating to inbreeding, is physical problems such as hip dysplasia, which affects all breeds except foxhounds. This can cripple dogs, and is extremely painful, and any dog that is in constant pain is likely to bite. Breeders are the main cause of these hereditary problems, but most just don't care.
Many people think that mongrels are best, and they have a point because most mongrels don't have a strong working instinct, and haven't been inbred. But exotic breeds are fashionable, mongrels aren't.