This video is supposed to be funny because the little dog thinks he’s protecting the girl from an attacker. What a brave doggy, he’s so tiny, etc etc.
[Trigger warning for dogs: Loud barking!]
Is the dog heroically protecting the kid from a perceived assault, like a miniature Marine? Maybe. Does that make everything okay? Not even a bit.
The kid isn't going to care whether the dog has delusions of heroism when he's in urgent care. His parents' lawyers aren't going to care when they sue your ass, either.
Think about it from the dog's point of view. Supposing his motivation really is to protect the girl (rather than the more likely, “I don’t like this unpredictable child, I need to make him stop doing scary stuff”), is that really a world we want the dog to live in? Where there are constant dangers to himself and his loved ones, and he has to risk his neck to protect them? That sounds like a conscript living in a war zone. Not cool.
Sooner or later, barking and charging isn't going to work. What if he gets yelled at or hit, instead of laughed at? What if the scary thing doesn’t go away like usual? If at first you don't succeed, try harder, right? Since there's no air support to call on, I guess our little soldier will just have to get a bigger gun. That just means escalating aggression, which means more stress for the dog and "suddenly" the owners are left with a "nasty little ankle biter". Whose fault is that?
Original video source: https://www.facebook.com/story.php?story_fbid=230998907273046&id=130245990681672&_rdr