Yep that's what the complaint was about for that dive shop on Trip Adviser. The DM was preoccupied.
I think making a special event dive (on a separate boat)to kill Lionfish would be popular. Tons of divers just itching to get a spear in their hands and kill something.
Put them all on a special Spear Hunting excursion charge a price comparable to local diving rates and rent them a spear gun.
sell the fillet to the local restaurants and give a prize to the best hunter. win win and win.
It would even be good business for the local doctors!!

White Sands Dive Shop
https://whitesandsdiveshop.com/