So, while a person who is on LSD is trying attack you with a hammer, your reponse would be polite conversation?  I agree 100% that violence must only be used when necessary.  I think actively being attacked by someone wielding a hammer counts as necessary.

With regards to "about a second after the taser"...  If you've ever seen someone get tased, you know IMMEDIATELY if it was effective or not.  There is no middle ground, wait and see, when it comes to a taser.  Also, "About a second", is that 1/2 a second, or 2-3 seconds, or what?  The problem is, without a full video of the incident, there's no way to know, but that is a very important distinction.  I doubt someone was sitting off to the side with a stopwatch.  

Overall, I agree with the point you're making, just not in this particular scenario.  Cops need to focus on de-escalation and help rather than violence.  But people need to quit crucifying every cop just because they happen to have a badge.