I agree that it was handled poorly by all that are involved, but there are three things that really stick out to me.
First, an officer or a judge will be the first one to tell you that ignorance of the law is no excuse for not following it. That must go both ways. Not knowing that OC is legal and drawing on the man is inexcusable.
Secondly, when a officer is in a tense situation (even though the officer made it a tense situation) and is pointing his gun at you ordering you to lay down is NOT the time to debate who is in the right and who is in the wrong. You follow instructions, let the situation be defused, and then sue the bajeezus out of the system if your rights were violated; a department having to settle a lawsuit will make much bigger waves of change than a street argument. My best friend is a retired sherriffs deputy and told me of the time a few years back when he was pulled over on his way back from hunting because his truck was mistaken for a stolen vehicle. He was spread eagle on the shoulder of the road, his truck searched and rifles laid out like a crime scene, and it stayed that way until they had finished running his plates and ID. He didn't try to yell "It's ok, I'm a retired cop, you have no right to pull me over, etc..." because he had been in these tense situations and knew the best way for everyone to be at ease was to follow along until things got sorted out. I think I would have been ticked enough to file a complaint, but he ever did. Guess he understands better than most of us.
Lastly, the charges brought up by the DA is one of the sketchiest parts of this whole story, if they would have offered him an apology, promised better training, etc. it might have been a step in the right direction. But trying to bully him through this stinks to high heaven.