Those statements are not mutually exclusive. Cutting down on the plastics we buy might still be one of the most effective things we as consumers can do even if fishing nets are an even bigger problem. Just like buying low-emissions cars might be an effective thing to do as a consumer even if most pollutants are emitted by industry.

The fact is that we need to address both fishing and consumer use. Over-focusing on either one could be seen as distracting from the other, but it's not particularly helpful to bash other environmentally aware people over it. The problem is the people who don't even know or care.