The public also has a right to stay still and follow the orders of the officer, then they wouldn't need to worry about getting tased.
I'm not a Pro-LE person, but if a cop tells you to do something, you are required by law to do so, or get tased/shot.
Every time i see some degenerate run from the police or fight an officer, i actually get joy out of watching them get tased or have their face planted into the pavement.
There are always exceptions, but the bottom line is that in America you have to follow the officer's orders or suffer the consequences, even if they are twisted.
Such is life, i see this in professional business practice on a regular basis, there will always be some twisted people out there.

Expectation..
As a cop, I have the expectation that you will do as I say. As a bad guy, you have the expectation that if you don't, there are consequences. The consequences should be reasonable and fit the situation. If you refuse to sign a speeding ticket, I do not have the option of tasing you nor shooting you. If you run, I have the option of catching you. If you struggle with me I have the right to overcome your resistance with reasonable resistance
It sounds strange but between cops and the bad guys are some unwritten rules. This does not apply to the rabid, pshyco nut cases out there, but for 95% of the criminals we arrest, there is an understanding. Some of the rules are like this..
If I go to arrest you and you try to get away, I will attempt to take you into custody quickly, explosively and as effeciently as possible, causing the lest amount of damage I can. You as the bad guy are allowed to pull away, push me, jerk around, duck and weave, I am allowed to slam you to the ground and get the cuffs on you and its over. If at any point you take a swing, or attempt to hurt me and not just escape, then I will be forced to turn up the volume and within reason, get very serious about getting you under control
We like it this way. It works most of the time. They (the bad guys) know the boundaries they can operate in and expect to not get busted up. We can move around in unpleasant areas and neighborhoods and not dodge bullets or fist all day long. When cops can't be trusted to live up to their side of the deal, then it can get pretty rough and its a lot of fighting bad guys a lot of the time.
In that teenagers case, he can expect the cop to chase him, he assumes risk when he attempts to flee. If a car is chasing a bicycle down city streets, through parking lots and over sidewalks close on his tail, bad things can happen. I don't fault the cop for accidently running the guy over, I fault him for planting a gun.