My first reaction, too, Amy! I admire the entrepreneurship, but it really seems like an unauthorized commercial invasion of public space which, traditionally has been quiet.
Definitely an invasion in my opinion. We go for the sunset, and since it's a magical time of day, we want to experience what the Eagles called "A peaceful, easy feeling." Not THUMP, THUMP, THUMP! But whatever!
It appeared to us that it was a gathering of family and friends. If you look behind the DJ there was a buffet like spread of food and everyone had drinks. So I guess they figured the lighthouse is proper party venue