Bypassing the "were they right/wrong", as a firearms user for over 20 years my judgement of the video is that the reactions of the Female officer during the firing of the taser were appalling.
If ever the police, during taser training, have to see a video of how NOT to fire a taser I would use this video. The little "jump" when she draws it, the "shoot form the hip" deployment, the panic in her voice and actions - all of these are the actions of an under trained, under qualified officer.
I remember vividly when tasers were introduced and it was said their deployment would be treated exactly the same as a firearm. In this same situation the officer would have shot the guy, does that seem proportional to the threat he posed?
I don't think it's a question of training or qualification. Some people just panic. The actions of a wpc on two occasions nearly had my step dad seriously injured or killed. I've posted about it on here previously.
You can have the best training in the world but it isn't worth squat if you can't keep your head.
Investigate, surely?! Find out where he lives, consult records... be sure of who it is so you don't have to ask in such a lucky dip fashion? Frankly their investigations sucked as they did get the wrong person. I don't think they should have the right to be so intrusive as to demand to know who you are on the spot and, in any case, they shouldn't be tasering those that don't comply in the face