I think the best solution for you would be to go with operators or groups that don’t allow spear fishing. There are entire Islands you can vacation to that won’t allow divers to take anything (including wildlife) out of the water.
I respect that you don’t like spear-fishing or other fishing activities while diving, however spear fishing divers have to be sure to check their operator allows spear fishing. if that’s an activity they plan to engage in. Why not do the same yourself, check if they allow fishing...but in your case you can choose to NOT go if they allow it, that way everyone’s happy.