What rights were violated?
The police have the right to detain you and to arrest you if necessary. He has the right to remain silent, have an attorney present during questioning. He does not have the right to resist.
The police do NOT have the RIGHT to detain you or arrest you unless they have probable cause or a warrant.
He had a right to not be assaulted by the police. If, like the video appears to show, the police grabbed him without first commanding him to assume an arrestable position and informing him that he was under arrest, then they violated his rights.
I know you dont, and won't, get this...but our police have a special place in our society. They are the governments arm for forceful coercion. They can arrest you, use (deadly) force against you or your loved on. We also give their testimony special credence; if the cop says you were speeding, and you say you were not, the cop will be believed. We NEED to have this special social contract with police because it benefits us all.
However with all of these benefits SHOULD come with extra responsibility. They need to wield this power carefully, and when they exceed it then they need to be held to an even stricter standard.
In this case, it appears that the police went active on a guy who was not given a chance to be arrested without violence. If that is indeed the case, then they should have been held accountable.