Punishing days at school

The last few days I have had a school issue that has been diverting me from fighting ills in the dog world!
Other mums or dads will probably agree that a problem at school can soon invade your every waking second.
I happen to believe in reward-based philosophies for most things. But 24 hours ago I felt sorely tempted to put that ethos on hold and do a bit of punishing myself!
This week there was a small incident on the rugby pitch, one boy tackled another who didn't have the ball. An altercation followed that spilled into the changing rooms. Unkind and heated words were spoken and near the end one boy was shouting at the other repeatedly and getting very close to his face. These are eight years old boys.
At this point my son stepped in and said something to protect the boy being shouted at, it was an admittedly an overly dramatic rebuke (I really don't know where he gets that from!).
He called the boy a "spiteful little brat."
(He later claimed this was inspired by the Chronicles of Narnia, but I've yet to test the reference.)
He was told to go with the other boys to the Deputy Head's office the next day at 10am. They were all told not to worry, that it would all be sorted out.
That night he was worried, he slept fitfully and he even found a watch to wear for fear of being late for the appointment.
I reassured him that he did not need to worry, he had stuck up for his friend and even though his words were harsh he had apologised to the boy both privately and publicly.
(I was actually relieved he hadn't sworn, or hit anyone or indeed lied about his actions when confronted by a teacher.)
He was still very worried.
The next day the first of the involved children emerged from school - the boy my son had defended. He had received no punishment.
The boy that had been shouting at the first boy - he had also received no punishment.
My son, however, received a caution for his behaviour - a little like a yellow card. A yellow slip of paper that is much feared. The first he had ever received.
He was stoical about this and had not protested.
I was by contrast furious.
To punish a child for standing up for another using just a rebuke to disarm seemed like madness - especially as the others' unkind words had gone totally unmarked. It was inconsistent at the very best.
A tense session with the teacher concerned revealed the facts I had been told were correct. That teacher is now very aware of what I thought of his very poor attempt at metering out justice. One of the other mums has complained, too.
I will reward my son for stepping in and supporting a friend and not support his punishment.
I'll advise my son to use less emotive language in future, perhaps drawing his insults from another author! But I am proud of his instincts and disgusted by the school.
We had a notorious bully at my little school when I was the same age as my son. He was huge, two years older and was always taking things off the little kids and pushing them around. I remember the first time he crossed me like it was yesterday. He pushed me off the monkey bars and I hit my head. I was almost as furious as I was with that teacher yesterday - I ran after the boy and started throwing punches although I had never been in a fight before. I was the smallest girl in my year so I don't think he could have expected my assault. Luckily he turned out to be a hopeless fighter and I quickly won and he ran away crying, his reputation as a bully in tatters.
Did I get reprimanded by my teachers?
No.
They just smiled, a lot.
Call me a rebel, but I'm really rather proud of my little boy. At least he only used words to wound - I had to resort to fists at the same age.