The training of dogs is another thing I find problematic. We are constantly told that dogs must be trained and controlled, this often seems to involve a dog being punished, and rewarded with food . All this time and effort spent attempting to alter a dogs behaviour and yet they still attack. Even dogs supposedly well trained and controlled still attack
Modern dog training does not include punishment, but focuses on food rewards. Training is one part of making sure that a dog is well balanced, but socialisation is the other side - making sure they have positive interactions with other dogs, children, traffic, vacuum cleaners, cars etc etc early in life. It is very possible to have a dog that's well trained and badly socialised. There are dogs out there that will roll over on command but couldn't be trusted around other dogs. As someone who inherited an untrained and undersocialised 14mo, I can assure you that training later in life is much easier to crack than socialisation.
The vast majority of people who have dogs with issues (usually rescues or the result of being attacked by another dog) ensure that everyone is kept safe - muzzled, on lead, yellow warning sign asking others to keep their dog away, quiet locations for exercise. However, you never hear about, and rarely see those dogs because their owners are successfully keeping everyone safe and are keeping away from third parties.
I would, however, heartily agree that the dog training and behaviour industry needs regulation - there are literally no restrictions on who can call themselves a dog trainer or behaviourist and there are some charlatans out there.
For example. Imagine an agressive dog that had trained with a particular 'toy'. Imagine this toy equates to aggression and food in the dogs tiny brain (dogs are not particularly clever or intelligent BTW). Any toddler who attempts to remove that toy from the dog is obviously in danger of being growled at, snapped at or "nipped' (whatever nipped means), at the least. It isn't hard to imagine how these situations can go catastrophically wrong
In much the same way as you teach your children to look before crossing the road, they should not be approaching strange dogs without permission, let alone trying to take a toy away from a dog.
If a dog was trained to be aggressive using toys in the way you imagine (unlikely) then you'd have to be a total moron to leave the dog with that toy unsupervised.
The old rules around dogs - let sleeping dogs lie, let the dog eat in peace, let the dog come to you not you to it, don't take the dog's toys away, don't kick the dog... All are still relevant.
It's also important to note that dogs can have an excellent sense of what is theirs and what is not. Mine will happily destroy a toy I have given him, but when he's met small relatives and they have soft toys he's ignored them - but if I picked them up and gave them to him he'd destroy those same toys he's ignored.
If you really wanted to train a dog to be aggressive in the crudest way possible you'd not take it out of the house for the first few months of life then administer pain every time the dog saw what you wanted it to be aggressive towards.