I'm going to look at this from both sides. What both cops did in both cases was overreaction and flat out wrong. But I think admonishing cops, (generally) who also get killed in the line of work and have very very high stress jobs isn't going to fix things either.
For cycle's two lines in (reading) my first thought is that she was pretty snotty. I've been pulled over. Many times. And ive always been polite. If you don't agree with your ticket you can go to court but getting snotty and rude with people who work on the edge is just stupid. It's like how I can't understand why people treat wait-servers like crap when that's the person who has control of your food. Be polite. Be reasonable. Usually there won't be an issue.
Second. Handling yourself during a crisis with adrenaline in your system sets you often on autopilot and rational thought can vanish. Especially without good training. Look at how rigorous navy seals train because we know they will be in intense situations. These days there are as many stories of cops being shot for routine traffic stops as well. They have to approach every vehicle on edge because they don't know what they will get. The guy in the video had been known already to use the weapon and commit crimes. The reaction was not right. I'm not saying it is. But fear, being amped up, running on adreline make for strong and powerful forces in our reactions. What we need to look at is are our cops really getting the right crisis training to deal with these situations to keep them thinking and responding smartly and calmly in the heat of the moment.
Saying we have bad apples won't solve it. Training and weeding out those who can't handle the stress is better. Ensuring that proper support post high stress incidents is occuring will help. Working simulations of all kinds of people at traffic stops, better 'hazard recognition' techniques as we call it in my Industry for who is just a snotty person and who is truly dangerous will help. And with excellent training, the grounds for disciplining what should be less cases will also be much firmer.