The Dorner case was awful and no excuse at all for that....I saw no problem with what happened in the garner case....I have received over fifteen tickets in my lifetime and have no problem with police enforcing the speed limit....citizens know the law and it does save lives.
I don't think anyone is questioning whether lives have been saved nor whether citizens are aware of the law. To the latter, certainly citizen awareness of statutes cannot serve to justify said statutes. To the former, the question is that, since speeding does not necessarily entail that one will injure others or damage property, is it just to hold up and take money from any person who happens to be driving faster than a given speed.
Let's put it this way: suppose you were able to see into the future and, further, see multiple possible outcomes of your action. You see someone speeding in the present and have the choice to either ticket them or let them go. You know, through your clairvoyance, that this person will never injure others or damage property. Do you still pursue and give them a ticket?
Many might be inclined to answer 'yes' for one of the following two reasons. First, it's the law and they broke it. This reason reduces to nothing more than rule-worship. Second, however, one may cite the deterrent factor involved in punishing this individual. The problem, however, with this way of thinking is three-fold: (1) plenty of us know the speed limit laws and the associated punishments, yet plenty of us (I'd say the majority of drivers) still speed, so deterrence isn't really working; (2) to make deterrence work, we'd probably have to make the current punishment harsher; (3) if we refuse (2), we are punishing this driver in vain, I.e., for no purpose; yet, (4) if we increase the punishment, now we are merely sacrificing one individual for the sake of "society". I think (4) is abhorrent and contrary to the ideals that led to the founding of this nation, as those ideals focus on lifting the individual above society.
Now, you might reject this thought-experiment simply because you think such experiments are mere fantasy play. Yet, when we actually look at the numbers of drivers, the numbers of those who speed, and the number of those who injure others and damage property, we can clearly see that it is highly unlikely to say of any one of them, taken as an isolated individual, that their speeding will result in any injury or damage. I.e., we find ourselves in a situation which very much approximates that of the clairvoyant in the thought-experiment.