You are assuming that the sources have the emails. The way I understood it, these sources are claiming to be memories of alleged former employees, so they probably do not have any access to CIG internal communications anymore, and its just "he said, she said" situation. In addition to that, these emails may contain personal information about other employees, not just about sources themselves, and it would indeed be unethical and unprofessional to publish them without agreement of everyone involved. Especially if the emails may contain some criticism of employee performances. You dont just publish internal comms because someone said you are racist with no evidence to back it up..
And in the end, the accusation about only $8 million of backer money remaining is much more serious, IMHO, because it would kill the whole project and could be an indication of fraud. Thats what CIG should concentrate on, and would also be easy to disprove. In fact, it would be a good idea to publish a rough overview of CIG expenses, it is one area where CIG is strangely silent, even tough rest of the development is pretty open.