If your taking the 'protect wildlife' route, then it doesn't make sense to argue against taking trash out of the ocean which directly kills a god-awful lot of animals as it stands.
Straining billions of sea creatures out of the top meter of water is an actual harm. It makes no sense to have to argue that's a net loss. Unless we're taking the 'save the large, cuddly animals first' route, which is so often part of eco-theatre.