> For example, if I was a black man and the teacher was white, my essays about slavery would be not about if I learned the material but my trying to work around determining how racist a teacher might be.

That would be a valid concern regardless or your or professor’s race.

And even if we take into account that people are more biased towards opinions that elevate them, we should also take into account what an average college history teacher believes in. At that point you should probably be worried that your view isn’t Marxist enough.