I suppose it’s open season on professors and teaching assistants. All grading beyond the trivial is more or less “arbitrary.”

I used to teach math to undergrads, and even back then the admin would never have protected me from this kind of social engineering attack.

Isn't this the kind of coddling that more conservative people decried? If a student doesn't produce rigorous work, grades should reflect that. This makes grades into something arguable, not a score a student can learn from, or an evaluation that employers can use.