The fact of the matter is that the rider should of expected a citation for the infraction of either reckless driving, eluding, or the attempt of, and or speeding.
 What he didn't and shouldn't have expected was to be hit from behind, and then basically assaulted by a kick to the chest, after having to pick himself up from the roadway. 
 The officer in question lost control of the situation, something we pay him for as a professional to gain and maintain, lost his temper, and basically assaulted a fellow citizen, dispensing some roadside justice.
 In the end he was not only rewarded, he was advanced in his career, and transferred to a more prestigious position, and we as taxpayers pick up the tab for such behavior.