下面的句子摘自2022新全国卷1阅读B：

In a world where nearly 800 million people a year go hungry, “food waste goes against the moral grain,” as Elizabeth Royte writes in this month’s cover story. It’s jaw-dropping how much perfectly good food is thrown away—from “ugly” (but quite eatable) vegetables rejected by grocers to large amounts of uneaten dishes thrown into restaurant garbage cans.

请问：food waste goes against the moral grain 是什么意思是？尤其是 moral grain 是什么意思？特别是这个 grain 是什么意思？