There are situations in which certain physcal limitations open a person up to great risk of injury, and to decline, say if you had a fresh surgical wound, would be prudent.
For the able bodied to not help the officer when asked to help becuase they might get hurt, leaves the officer to a near certainty of getting injured. That "oh I might break a nail" attitude to me is the hallmark of a pu$$y. I guess this is what happens when people are raised on "conflict resolution" instead of good old-fashioned knuckle dusters on the playground.
Had the officer not requested his assistance, I would agree that he might have been considered a threat by the officer had he just jumped in, and it would be better not to. THAT could get someone shot.
I guess there are two types of people in a pinch. Those who run toward trouble to lend a hand, and those who run away and do not even look back.
As for risk, if I waited for everything to be sure and safe, I would never get in my car.