And, to turn your logic on you, because you've never been there you can't possibly seem to grasp it.
A dogs life, no matter how emotional you are, is still that-a life.
You raise it, you make mistakes, sometimes the mistakes bite you in the ass (literally) and you are now faced with the question: what did I do wrong (see: if you don't train me, don't blame me) and what do I do now OR should we throw in the towel and kill the dog?
You look at the dog, look at your photos, look at your videos, review the trips you've taken, the milestones you've passed, the mistakes you've made that they've forgiven you for and you weigh your options. Do we go forward and change our lives for the better or do you give in to the easy route and ask someone to kill your dog for you knowing that you've likely caused this and you're likely teaching the next generation how invaluable a life is in comparison to the work it will take admitting you messed up and are now responsible for cleaning up the mess.
This dog in question was likely not born aggressive. It may have offered a guarding behavior as a puppy (most every pup will try unless mom and siblings have beaten it out of them) and someone fought them on it. They teased the dog thinking it was the right choice and they then turned it over to a trainer with a mentality much like yours who tried to beat the fight out of the dog, just like in humans you cannot beat the fight out of every dog, instead of fixing the problem they made it worse, and worse, and worse.
Had anyone had the sense of mind to make humans near the bowl a positive thing at the beginning (or middle or end) we wouldn't be seeing this video.
There are so many easier and more humane ways to handle dogs and humans that it break my heart and hurts my head when people jump to the abuse for foundations or to clean up a mess they created.