It is definitely not ok. But he's made his stance and his point quite clear and I'm afraid no amount of arguing with him is going to change his mind. It's only going to get you into further trouble and into his bad books. He might even cite your behaviour as evidence that what happened at the camp was just some students who were out of control and refused to listen to the camp coordinators.

The professional opinion of both Professor Donoghue and I is that it was a dark hex and that none of the students are to blame. I'm sending an owl to the Ministry right at this moment to ask for an explanation, but accusing the Ministry in front of the High Inquisitor will not change anything.