That video could have been filmed on my local closed down railway line turned cycle track. Despite numerous notices saying keep your dog on a lead nobody does and the owners only get concerned when the dogs start fighting each other.

When I go running down there it's normal (or usual anyway) to have dogs rush up at you like in the video - not a pack of 25 I admit but often in twos and threes. Some are friendly but some are downright aggressive and it's hard to tell in advance which are which. I think the aggressive ones see you as prey, particularly when you're running away from them. If you ask the owners to control them you either get a mouthful of abuse (men) or a "it's just being friendly" response (women).

A couple of years ago I was running with a group on the trail and we had three little terrier things snapping and growling at us for about 1/4 mile until they were too far from their owners and turned back. A minute to so later a couple of mountain bikers passed us going in the other direction - followed shortly by a loud yelping noise. The dogs had gone for them and one of them had been run over. It was only at that point that the owners took the slightest notice. Fortunately neither of the bikers were hurt and I couldn't have cared less about the dog.

I know the original post was about dogs in Morocco but in my experience it's no better or worse there than in many other places. Of the two worse dog attacks that I've experienced on a bike one was in Mauritania and the other in an affluent part of Pennsylvania. On both occasions they were large dogs that came at me from their property when I was riding past slowly and both of them meant business. The US one was a particularly aggressive animal that tried to attack the back of the bike when it couldn't reach my legs.