Well, it's both.

"The southbound man moved to one side and stopped to allow the other rider to pass, as is convention. But instead of whizzing by, the second cyclist stopped and allegedly punched the first man twice in the head. He then put him in a chokehold, according to police, and punched him six to eight more times before riding away." is the victim's story, and the idea that it was due to the salmoning was from the police.

Maybe I could have been more precise in my language, but "if the victim's story is what really happened" and "this really was about the salmoning" were intended to be separate statements that stand on their own rather than "if the first is correct then the second".

Personally, my guess is that there was more to it. Maybe the victim didn't move to one side and stop and he expected the other guy to stop. (It's always "I was just minding my own business, officer!") Maybe the victim insulted the other guy. Maybe they collided.

After all, if this path has much traffic, the odds are this wasn't the only salmon he encountered.