Being a news outlet they have the right to protect their sources. Just because they don't tell you who their sources are, that doesn't mean their sources are not legitimate. If these people are eyewitnesses or have any other firsthand knowledge of what is going in, then the station does have supporting evidence. Just because you don't want to believe something, that doesn't mean it isn't true.

If these accusations were not true, then the people would would be adamantly proclaiming their innocence.

I don't see that the station was wrong or unethical in bringing this corruption to light.