Hmm, completely different stories between the news coverage and the actual dash cam video. From the news footage alone, the pickup seems to completely be the innocent victim, who was actively passing a big rig but the Camaro was just too impatient. In the early bit when he blocked the Camaro from cutting in if you pay attention to the shadows on the ground you can even see there was a vehicle in front of the pickup.
Watching the full length video, we can then see the pickup didn't complete his pass and held himself next to the big rig. We can speculate this was on purpose to block the Camaro, but not having a view of the speedometer or knowing the speed limits on that stretch of roadway we're just speculating. Just as possible the big rig is the one who sped up and the pick up didn't want to speed in order to complete his pass. It does happen.
All in all though, they made the right call in saying the Camaro was at fault. Aside from the stupidity of his actions, he was found to be impaired after all.
The only fault to the pickup was if he purposely slowed down just to block the Camaro. It's entirely probable, but it is an unknown. I've known of at least one case where a group of big rigs were actually praised for such a move. A person I know's son was killed by a hit and run drunk driver who was later captured thanks to a few big rigs that collectively blocked it in and forced it to stop.
Now, on the subject of people who just drive in the left lane. At least in Ontario, unfortunately, it's not illegal. I haven't found anything in the Highway Traffic Act against it. I hate people that do it, but without it being against the law there's not much that can done about it. In comparison, my German colleagues once told me that over there it is illegal. Failure to move back to the right once safe to do so or passing on the right is a major penalty (they didn't enlighten on what 'major' actually meant though). Over here, it's become so common place my niece once told me she thought the left was the driving lane and the right was meant for merging and passing.