The truck he had pulled over was with the bikers, videoing them. It had been blocking traffic, and taking up two lanes. The truck and the bikers were acting like ass****s. And yes, failing to move over to the left away from the cop was illegal. Didn't look like the rest of traffic was moving over either, the line of trucks and cars behind the bikers weren't starting over UNLIKE the bikers who were mostly to the far left of the lane already, and slowing down. I think the reality is, he was frustrated because he was unable to do anything about how they were riding, and vented his frustration by spraying them. He certainly didn't look like he was afraid of being hit when he jumped out of the car. His actions caused several to swerve, risking an accident. It's all very well to say that it would only be on the outside of their gear, and wouldn't do anything until the stopped and took it off, but then why do it? Because he knew they would avoid it. He risked an accident by doing that, had one swerved into another. And that leaves aside what if one had gotten into their mouth, and became to distracted? What if one got it into their eyes, and was unable to see? And fiver were treated there, and one sent to the hospital. If you or I stood on the side of the road and sprayed a group of riders because we didn't like them speeding, etc., we would go to jail for assault. It wouldn't matter if they were breaking the law.
Me, I like the police. I support them. I don't support when one uses excessive force, or acts in ways contrary to good society. Bad cops make all cops look bad, even though they are a small minority. I certainly don't want to live in a country with no police, but I do not accept living in one where bad cops are protected.