I think what this quote is responding to is people disseminating some first world millennial's first uninformed guess about an issue as if were a revolution and a blessing to the world, instead of stopping to think that their precious intellectual virtues are not limited to people of their class, education, and supposed intelligence.

The idea that our enlightened attitudes set us apart from the rest of unwashed humanity is our fake news -- the stuff we consume unreflectively because it flatters us and plays nicely with our prejudices. Presented in a neutral context, the idea that the agricultural industry was throwing away significant quantities of produce because of aesthetic flaws would meet a lot of skepticism. Presented in the context of you are special because you understand how wrong this practice is and special people like us can help save the world by fixing this problem the idea gets uncritically accepted and widely shared on social media.

Calling people "classist as fuck" is designed to startle and threaten exactly the people who tend to accept these narratives uncritically, and put them in a frame of mind to consider that they might be wrong. Whatever the truth of the issue is, we won't get there unless we stop seeing ourselves as the hero of the story.