This sound like a neighbor dispute. Concerts? Yea, thats not an airbnb thing. And a campground? Yea, he'd need a permit for that. Don't hate on some little guy supporting his family renting their ADU because this aint that.

And if I'm reading this right, nothing has actually happened yet. He's paying for a mound system, you were notified per the permit regulations and you start freaking out online. If he has parties, join him in celebrating or grow up.