What should I do in about this work problem?

I work in the cafeteria at my school. Today, I overheard one of the chefs, “D,” talking to one of the workers “C,” and they were talking negatively about another worker, “M,” while he was there, literally ten feet from where they stood. I’ve noticed that he is treated badly: the same chef treats him like he’s stupid and is always yelling at him or about him. I think a big part of this superiority complex of hers is that the he doesn’t speak English all too well (though he can understand it). I talked to “M” afterwards and he told me they were always like that, and that he didn’t care to do much about it so as to not cause any problems.

Afterwards, another one of the ladies (“L”) asked me about what “M” and I were discussing. After telling her, she confirmed that they were always like that, but that it wasn’t just with him. She said that this chef talked about everyone there and treated them the same, and that the main chef, “P,” also partakes in this treatment,treating them more like animals than humans. And I realized it was true- I have seen him yelling at some of the workers there for the most minimal of things and

Anyway, I have seen this treatment with all the staff there- the ones whose primary language is NOT English (“C” is the only one there who speaks English primarily, and is never yelled at). They get pushed around, yelled at and treated like they’re dumb, which really, really bothers me. The only person (“P”) I can think of even mentioning it to seems to be a part of it. I want to do something about it, but I don’t know what. “L” said that even though there were negative aspects, there were also positives, and that while she did wish she could do something about it, it could be much worse, and it wasn’t worth it because the workers like their job for the most part. Given that, I don’t even know if I should do something. Which course of action should I take? Am I even in a position to do something about it? I’m only a student worker and not a permanent staff member.