In my opinion it is not in itself a strange idea to engage a mediator. Then in a fair way; that is to say, then the player also has the right to see all the evidence here. It's his own account, so he has the right for this.
The reason they provide now that they do not want to give the information because they are afraid he will cheat again is not a common and valuable argument.
If he did something wrong, and you can proof this, then it is easily to close the case and then Betcoin is absolutely in his right.