Last night, rock band Linkin Park visited Bristow VA. During the concert, they had a giant screen behind them that streamed live tweets from the concert attendees.
The picture above reads "Pie is the best!" This was likely a response to this:
The photo is a bit blurry, as it was taken in a rush, but it reads Fluttershy is Best Pony.
Video from the concert is starting to pop up on YT, so I'll keep my eyes peeled for a video of the tweets.
Huge thanks to Caisius for snapping the pics!