It's all too easy to say what you would do in the same situation, but as
@classic33 says, "hindsight is a wonderful thing."
The OP would have been quite happy walking along when he's confronted by three blokes demanding his bike, it's not unlikely that he might have thought there was a bit of violence coming up.
How many can honestly say they would be able to think logically?
I was once the victim of an attempted forceful begging/mugging attempt.
Luckily the guy delayed, and talked bollocks for long enough to loose the element of surprise, for me to get my shoot together and square up to him.
Eventually he backed off without the need for fisticuffs, until he was about twenty yards away when he started to tell me how lucky I was and what he would do to me next time, all whilst walking in the opposite direction
