Clear the airspace for law enforcement aircraft. Happens a lot when something big is going on.

http://tfr.faa.gov/save_pages/notam_actual_4_2599.html

and news helos from three different affiliates trying to muscle in on the same tiny patch of airspace...

what better to open the evening news than aerial shots of the drama as it unfolds.

That was what came to mind after I read your comment. (And, BTW, why I deleted my initial, immediate response)

I have a bad feeling that any demonstrators are going to be dealt with very very harshly, with no media or whatever.
The only other option is if they think the rightfully angry people have SAMs.

from filming the area.

2 miles from StL International Airport.

This thread.

as to why air traffic would be shut down more so than a media blackout.

of flying over gunfire while approaching Lambert to land?

I think it is more fear mongering than anything. I think the cops don't want the media there, for two reasons, to avoid having air traffic in their operations and to avoid having media capture what they are doing.

I mean, clean-up operation.