The quality of this video is terrible, so let's go to its description:
"Eagles Game 12/20/2009 - Pittsburgh Steelers [fan] stands up and takes a few snowballs during a game."
If you go to an opposing stadium to watch two different teams other than your own while wearing your team's gear, you have to expect to get heckled. If it's snowing, expect snowballs.
The guy knew he deserved the onslaught, and chose to accept his fate head-on rather than trying to get out of it. While he looks like an idiot for (apparently) wearing Steelers gear to a 49ers/Eagles game, he gets some points for not shying away from the inevitable bashing.