His job was to clear a space for the paddleboat. They were assholes not to move. And when he's telling them to move the dude sucker punches him. And then outnumber him and beat him.
And the one white dude owns a mini mart and allegedly posted. I don't need your money. White dollars are superior. Sounds like some racism might be present if true.
Oh, I agree they were in the wrong and I didn't know that about the mini-mart guy. He did untie their boat and moved it forward, I think it tapped the boat in front - I'm sure that escalated the situation some (of course they left him with little choice).