That would be far more fair than not giving these graduates what they earned because of the actions of others.
If the people cheering really are disruptive, have them removed. However, unless the graduate is acting disruptive, the school has no justification to punish them.
If they can't figure out that it isn't reasonable to punish someone for the actions of others, then they have no business administrating a public school. Fire them.
But, but...this is their modus operandi for everything--punishing innocent people for the actions of others. Good for you if you succeed in getting any of them fired! School boards are deaf, dumb and blind.
I know of one school administrator who has an uncontrollable, explosive temper. I am praying that one day a student or parent will tape her tirades and put it up on YouTube for the whole world to see.
Meanwhile, the principal could have handled this properly by reiterating, at the very beginning, about disruptive cheering and that those who do so will be asked to leave. The administration shouldn't hold back a student's diploma that he or she rightfully earned...this is typical of their zero-tolerance, abuse of power, control-everyone-at-all-costs crap. No wonder administrators get no respect...they haven't earned it.
As for air horns, they shouldn't be allowed at graduations, that is a no-brainer.