This is a horrific act of cowardice.
The boys who are guilty of this assault are claiming that the referee directed racial slurs at them just prior to the attack.
The referee denies this.
Even if the referee said something racially offensive, you don't physically attack him.
Even if you choose to attack him, you never attack an opponent who is much older than you and not equipped with the same body armor and helmet that you are.
Even if you choose to attack an opponent who is older and who isn't equipped with the same body armor and helmet that you are, you never double team your opponent.
Even if you choose to double team your opponent, you never attack someone from behind like this. Stand toe-to-toe with the man - one on one - and slug him if you must, but never creep up on an unsuspecting person from behind and spear him with your helmet.
You'd be an idiot and a fool to do so (and would probably still face criminal charges), but at least it would be the despicable act of cowardice demonstrated in this video.