To be fair, this is done all the time when a concert is given in an arena so that nobody is seated behind the stage. I'm sure it was also done as a security precaution as well.
However, no excuse for the empty seats in front of the curtains. Oh wait, yes there is: The Clintons were on stage.
Curtaining off an arena for rock stars may be warranted....but when its the Clintons, that needs to be emphasized.
When the “cancellation” story first came out, I checked out ticket availability for this venue...just curious. Seating chart showed that seats in part of lower level (behind curtain?) and entire upper level would NOT be used.