The cop dropping him on his face was horrible, but AFAIK everything up until that point was the correct course of action. The kid was refusing lawful orders. If a cop asks you to do something (which is what all the 'border' checkpoints show, often with clever wording), you can refuse. If a cop orders you to do something, you can't refuse.

Before someone comments about lawful orders, it's a complex topic and you're welcome to fight it in the Supreme Court, but in general I'm just going to obey police orders.