frank, I think most people see where you're coming from and agree in principle (remember, this is a discussion about an actual event, not moral ideals), but you're picking a bone with someone who clearly had good composure in the situation and dealt with it very reasonably, without self-glorification or gratuitous violence. You've either failed to understand the place for ethical debate or vainly deny that violence is an inescapable part of life. In this case, very mild violence was used to prevent theft and detain the dude till the cops came. This is more honorable than what you could expect from the vast majority of citizens. You also seem to ignore the role of malicious intent, which seems to be completely absent in this case of "violence".

Also, discussion of ethical absolutes can never completely jibe with the adrenaline-laden reality of experiences like these. That point that the thief wasn't even following standard I've-been-caught-so-time-to-run procedure (arguing that it was, in fact, his bike?!) makes it impressive that the confrontation was ended with no more than a throw-down.