Even in the era of widening partisan gaps, it would be ill-advised to throw around indictments willy-nilly. Voters use James Comey's statements for the insights on Clinton's fitness for the presidency, not prison.
Classification is important; state secrets do need to be guarded. But more important than classification is government transparency. Classification in a democracy must be used judiciously and sparingly, else democracy itself is imperiled.
Overclassification actually threatens national security by limiting the sharing of information among officials and agencies. More fundamentally, overclassification undermines the critical ingredient for a well-functioning democracy: an informed citizenry.