If you're going to make the case that Hillary Clinton is not fit to be President because of something that her husband did as much as 40 years ago. Then you factor in that this issue has been vetted for 40 years by the media and his political opponents prominently. At that point, where's the evidence is probably a valid statement.
Also keeping in mind that the Clintons have been accused of murder, bribery, and just about everything else and you start to wonder who's crying wolf here. 5 months ago we were talking about her going to jail over e-mails but nothing has come out of that yet. Or Benghazi.