I'd say the opposite. Don't boycott him, patronize the buisness! Be a customer and when he asks where you heard of his buisness tell him as if he never did anything wrong that you saw his truck around town. When he honks again yell "Hey Charlie" (useing his real first name) as familliarly as if you've been best friends forever. It's harder to be randomly jerkish to people you know. If he keeps honking invitie hime to a bar-bq and say 'hey Charlie whats up with the grumpy driving? Everything okay at home?"
I've worked, drank and lived with some rednecks that were anti biker. I've been to their works x-mas parties and rode my bike to thier houses. And yeah, i've changed a few opinions. A couple people were anti-biker 'cause tehy saw us as elitists and sports yuppies that want to 'play' in the street. Finding out that i'm a nice guy and a cyclist and just a regular joe on his way home from a long shift helped change people a lot.

You CAN change people's opinions, but you'll seldom so it by an adversarial stance. That meks people dig in more. Get into their world and show, don't tell. And they'll usually understand.