In EACH of those video clips, they show the end, not the whole confrontation. Also clips can be edited. Remember this, each time it is the citizen that sets the level of confrontation. Otherwise everyone would then have to worry about the police going off like that, yet everyday, 24/7/365 the police have 100's of interactions with citizens and 99.9% do not end like that. When people get all crazy or commit crimes, most citizens do not get involved, they call the police, because it is not easy to confront someone. It is very easy to sit and judge. If you feel that way, the next time the poop hits the fan see if you can handle it without the police, I will bet the police get called. They are out there everyday putting their lives on the line for people they do not know, and in most situations, the police get hurt more often then the citizen. Go look at some police videos that show the entire confrontation. If the officer acts in a criminal manner, the department and the officer get sued, and the officer gets charged (by other police).
NO police department in the US would inject drugs into citizens. Maybe it could be used for unruly prisoners at a hospital, for doctors to use to administer drugs, so that they would not have to have the handcuffs taken off and endanger the hospital staff.
I have volunteered to be tazered and it wasn't that bad. When the power stops, it is over with no lingering effects. It is not like on TV. It just tightens the muscles. They use the same idea for healing muscles and nerves, just to a lesser extent. http://www.tensunits.com/