In my view he should have been properly vetted before being entrusted with the care of that beautiful animal whose only purpose in life is to look after him.
You gotta wonder how he passed muster, although maybe he just didn't seem likely to lash out like that. It now occurs to me that we don't know why this dog refused to cross- did he make a mistake, or was there a hazard? Either way, I hope he can get over being attacked like that- shame for all that training to go to waste. There are probably more worthy handlers waiting for guide dogs, and as you point out, a dog with a job, for which he is praised and rewarded, is a very proud and happy dog. There's a little wolf inside every dog, and they yearn to fit in their proper place and do their specific job for the good of their companions and themselves, asking only for their share of the day's spoils and a little affection.
A chap that lives near me trains blind dogs. I see him out in all weathers teaching them their trade. It's wonderful to see but only one dog can be trained at a time & this takes many months. I hate to think of one of them ending up with someone like this.
That's a noble trade, training guide dogs... and he must be a very patient guy who loves and understands dogs.
I'm always moved and impressed by working dogs; wish more people were as cheerful, dedicated, and competent as the average professional dog. Everybody realize how many other jobs there are for dogs? Rottweillers are still used for herding cattle (!) and hauling little carts, as well as guard duty. Then there's the famous Welsh sheepdog, one of many other herding breeds. Dogs are used for tracking and apprehending criminals, finding corpses, sniffing out explosives and contraband, finding and rescuing victims of kidnapping and disaster, cheering up people in hospitals... they've been invaluable assets to military forces in combat (who better to have on point in a patrol than a soldier with eyes, ears, nose and stealth like that!), and in addition to leading the blind, they also help the wheelchair-bound. I once saw a one-legged man in a wheelchair shopping at the Home Depot- his assistant was a three-legged Labrador retriever!! The dog carried things for him, and may have been trained to reach for items that were pointed out, although I don't recall seeing that trick.Most "mobility dogs" can, however, open and close doors. Obviously those two were helping each other: not only can that dog survive with 3 legs, he has a job!! And how about the recent discovery that some dogs can somehow sense an impending epileptic seizure, and alert their master in time for them to prepare themselves? There are already training and placement programs for such canine helpers.
My Peg is too spoiled and silly to learn a proper trade, but she enjoys her little chores: cleaning up spills, keeping the cat in her place, alerting us to people at the door, and warming up sofas.
When she's naughty (which is rare), she may get a good tongue-lashing, but even when she is at her worst I've never given her more than a light rap on the snout (maybe twice in seven years) and would certainly never bite her!!