This won’t be the most popular post here, but ...
The cops probably saved him from serious injury or death. They tried to get him to leave, but he refused. The crowd was already turning ugly toward him. When they started chanting Obama! Obama! Obama! the police cuffed him and took him away - to safety.
All it would have taken to turn the crowd into a rioting mob would have been for one Obama supporter to get physical. The man would have been stomped and a full scale riot would likely ensue. Some people like to celebrate by smashing windows and burning cars.
They are still on a "high" from the Phillies winning the World Series, and this could have escalated into a full scale riot with a lot of cops getting hurt.
Philly is a mess, to be sure, check out the you tube vids of the New Black Panthers "protecting" polling sites:
National Black Panther (NBP) goons intimidating white poll watchers in Philly:
http://www.youtube.com/watch?v=yd_5SlP8IpQ&feature=related
NBP thug exhibits his highly developed intellect and integrity:
http://www.youtube.com/watch?v=ek78MhY84xs&feature=related
Philly cops show up to deal with the situation:
http://www.youtube.com/watch?v=WTtk4iXv_xY&feature=related
Sorry about the links, I have to get to work this AM, so cut and paste.