A Clinton defender will inevitably set the bar for "substantive evidence" astronomically high.  They're like a cult in that way.  A fair exercise would be to turn the tables and pretend the person in question were a Republican or just not a Clinton.  Well we know what happened when David Petreus mishandled classified information.  I'm not sure what specific evidence they want to see before they'll accept that the Clinton's play fast and loose with the law.