It needs to be said that Paul doesn't have much use for the State Department.
In his own budget proposal for 2011, which called for a half a trillion dollars in across the board spending cuts, Paul proposed a $20 billion cut to the State Department. By way of comparison, the State Department's core budget for the 2013 fiscal year is $43.4 billion. You can see that provision of his budget at the bottom of the page here.
The U.S. security failures in Benghazi were serious. They shouldn't be downplayed or dismissed. But you don't have to pretend there wasn't a State Department failure, in order to conclude that it takes a lot of nerve to sit there and rip a secretary over the decisions made about how and where to deploy security resources when not only is the department chronically underfunded and having to make do, but while you yourself have called for slashing the departments budget by nearly half. That's not serious. And neither is Paul.