Oh I'd be a certain level of pissed, certainly. Mick has always struck me as a rather immature guy who likes to push people's buttons. I've had to learn not to get mad at him and not to play his games, but he certainly does it very well. I completely believe that he had a "shit eating grin" on his face, and it doesn't surprise me in the least.
At the same time....if what Mick said is true: the guy ran a stop sign. My personal experiences have been that bike riders aren't the smartest people out there, and can be pretty arrogant when they want to be. And then the guy swung a bike lock at him.
Now, assuming Mick tried to help him up (for the record, I only read the first page of this thread), whether he had a stupid grin on his face or not, just being a smart ass to someone is not a license to just take a bike lock and start attacking them. It's not very mature, but it's not a crime.
In the context of that, I'd probably punch the guy too. And I'm the kind of guy that doesn't stop at one punch.
So the moral of the story: don't run stop signs and then attack someone who stops to make sure you're okay with a bike lock. Grinning isn't a crime. It's not very mature, but it's not a crime.