It would have done him no good to fight the guards, regardless of his ability. He's shunned as it is due to the false rape charge, so fighting the law enforcement openly would only make his situation worse. He might even be banned from entering the city, which would prevent him from selling his loot and buying gear from the understanding blacksmith.
His mistake was to stick around in the first place. He should have only collected the reward, surprising enough they even decided to give him any, and then immediately hit the road. Staying there was only asking for trouble, and trouble he got.