People react badly to anonymous accusation that rely solely on the word of the accuser. Because, indeed, it's impossible to evaluate this situation without know

People react badly to anonymous accusation that rely solely on the word of the accuser. Because, indeed, it's impossible to evaluate this situation without knowing how trustworthy the accuser is. However, if the accusation is backed by the documents, nobody cares that the accuser is anonymous. Deep Throat has been anonymous for 31 years, and still his information has immense value. If you say "I heard X say Y" then maybe you're lying, maybe not - we shall see who you are and whether we could trust you. If you say "I've got a recording of X saying Y, made in a way that makes it extremely hard to fake" - nobody cares much who you are anymore, everybody cares about the recording now.