I see two different problems here.
First, is whether or not the rule makes sense. Second is punishment.
I'm not arguing that the rule was correct. I am only saying that if the school has a policy and then go back on that policy because of social media, then it sets a bad precedent. If the kid knew the rule, and knew the punishment, then the school did nothing wrong.
If the kid thought that the rule was wrong, he should have spoken out in a different manner.
I believe that if you break the rules, whether you agree with them or not, you deserve whatever the usual course of punishment is.
A good example is the speed limit in Bartlett. Stage Road goes through Bartlett. It is a 5 lane highway and has a 45 mph speed on either side of Bartlett. But the Bartlett part is 40 mph. I think Bartlett does it for monetary reasons. But I don't protest that by speeding through. I do the speed limit.