I think you're overestimating the dolphins here. Even humans have trouble not placing collective blame on groups of people they don't know well - it even has a name in social psychology, the "out-group homogeneity effect". Just think about opposing political groups or international relations.

So you think you’re not responsible for the fucked-up oceans because you let other people throw your trash into the sea for you, and the organically farmed salmon you eat surely wasn’t produced under atrocious conditions?