I agree with you. What I've seen happen is someone in cardiac arrest after being tased.
I did watch the video, although it's unclear if the recording started before the inital taser jolt. In any case, telling him to stand up and tasing him when he doesn't is stupid, since he may not be able to. And while some may think tasing is appropriate for backtalk, I don't.
I spent time (in training) caring for those who were incarcerated. One guy walked in without a mark, mouthed off, and I and a colleague spent the next two hours sewing up lacerations on the guy's head. We weren't very pleased with those officers. Like any other profession, there are officers interested in doing their job, and some who just like to prove how powerful they are.
I recall studying a method we performed on patients suffering various forms of pyschosis...shock treatment.
I guess shock treatment is for everyone now.