First off, sorry you got bitten Toddy.
Regardless of whether or not the owner should control his dog (yes) we should remember that dogs are not furry humans. They have their own way of doing things.
Have to agree with that. Dogs are dogs. Domesticated and socialised to humans (mostly), but they are still dogs. They are pack animals and they have instinctive rules of behaviour. We break their rules constantly, by the way we treat them. We expect them to understand our rules and act accordingly, but our rules are very strange to them. Some get it better than others, but in all cases, our idea of good dog behaviour isnt their idea of good dog behaviour. If the dog is well socialised, it will view all humans as being Alpha ...or at least above them in the pack hierarchy, but some dogs require humans to earn their place above them. It's fairly easily done if you understand how a dog thinks. I would echo those people who recommend watching Cesar Millan, the bloke is truly gifted with dogs. He uses their instinctive rules of behaviour to convince them he is Alpha. That doesnt mean he has a paramilitary relationship with them, far from it, it means he uses their body language and rules of interaction to socialise them. He works especially with big, bad-tempered animals and his results are astounding. Really worth watching.
It sounds like this lads dog is badly socialised. Ceasar would say the dog doesnt see the lad as Alpha, because if it did, it would of left the lad to deal with you and followed his lead. Pack dogs are led by the Alpha, always. They never take the initiative themselves. By dealing with you itself, it was taking the role of Alpha male. You dont want an Alsatian that thinks it's Alpha. This is the lads problem and he will have discipline and aggression problems with that dog untill he exerts his dominance over it and convinces the dog he is beneath him in the pack (the pack being him and his dog ...or rather, the dog and his human). If the dog saw the lad as Alpha, he would of had no issues with you petting him, because if you were a threat, the lad (the Alpha) would of sorted you out.
You (we) dont know when we approach a dog, if it's taking an Alpha role, hopefully most dont, but some certainly do. As said earlier, by not looking in it's eyes, not acknowledging it and not petting it, you take a superior role in dog language. That's what Alpha dogs do, they ignore the others. Junior dogs suck up, Alphas dont. If your initial contact with any dog, is like this, then they all should see you as an Alpha-human (except maybe the really mental ones) because your dog-language is telling them, that's what you think you are, they pretty much all should defer to this. Once the ground rules have been established (only takes a few moments), then you can usually interact with the dog safely.
In most cases, this isn't necessary, because most pet dogs dont play the Alpha role. So you are not something they need to assess and deal with as pack leader. You can approach most dogs with as much enthusiasm and ebullience as you like, they wont view you as Alpha, but they are not Alpha either so all is cuddly. It's worth remembering this, for those times when you meet a dog you are unsure of. Act like an Alpha and you will control the dog, rather than the dog controlling you. Head up, strong and confident countenance, completely ignore the dog, no eye contact, no petting, totally calm and indifferent. You need to believe it and "project it". Let the dog do it's thing and just ignore it. If it sees you as Alpha, it'll suck up to you straight away and all will be well. If it thinks it's Alpha, it'll see you as another Alpha and will have to decide either to submit or to challenge you ...there can only be one Alpha. If it submits to you, it;ll suck up to you. It may bark and growl for a bit, just ignore it, eventually, it will probably respect your indifference and submit. Job done. If it's totally mental, it'll probably go for you anyway, so stay out of range till you know what you are dealing with. Very few fall into the totally mental category, though there are some well screwed up dogs, thanks mainly to us messing with their heads. Most will still acknowledge their instinctive codes of behaviour though.
When you got bitten, this is what happened in the dogs head....
You approached his pack (him and his inferior human). You went for his head and touched him without permission. He evaluated you and decided this was not the proper greeting of an Alpha and he didnt need to submit to you. Then you turned to a member of his pack (the lad) and he did what he is genetically programmed to do as pack leader, he reminded you who was boss. The problem was not yours obviously, the problem was the lads for not socialising his dog properly. But you got bitten and there are a lot of dogs out there like this of all shapes and sizes.
Dogs that "protect" their owners, are in fact Alpha dogs, protecting junior members of the pack. It's a behaviour that owners often subconsciously encourage. Junior pack members never protect the Alpha, it's always the other way round. With little yappy dogs, it's not such a big deal, but owners of powerful dogs really need to get on top of the who's boss thing.
It's not all that simple of course, but you get the idea.