As a rule ive never seen a cop pull a taser as routine...
Lets try and look at this objectively.
The guy was driving and saw a cop car behind him. (It doesnt mention whether the lights were flashing or not - but lets assume they were - i mean, why else would you pull over?).
The guy pulls his car over and then jumps out.
Now for a police officer, when you pull someone over they stay in their car, you walk up, you have your chat and everyone walks away happy (or as happy as the driver can be if he/she's just got a speeding ticket!)
But in this case, the guy jumps out of the car straight away.
For the police officer that means one of two things a) he's making a run for it (in which case your out of the cop car with weapon drawn as fast as possible to start chasing them) or b) the person is being aggressive or has something in their car they dont want you to see. Either way i would probably be pulling my taser here as well.
It appears in this case that the guy got out to go to a friends house and after this became clear, the cop lowered the gun and was putting it away when it discharged. For me, i see no issues here.
What i do have an issue with is the automatic police reply that the guy was acting "aggressively". Is it too difficult for the police to stand up and say "Look, the officer drew his Taser because by jumping out of the car as soon as he was pulled over, the officer thought the victim might be aggressive. As soon as this was identified as not being the case, the officer lowered his weapon which accidently discharged striking the gentleman. We're sorry it happened, but thats life."
A bit of honesty like that might bring a bit of trust back to the cops, dont you think?